Grails exception after changing UrlMappings.groovy

I got this strange exception after changing the UrlMappings.groovy in one of my Grails applications today:

 plugins.AbstractGrailsPluginManager Plugin [controllers:2.1.0] could not reload changes to file [/home/tchan/repo/privategram/grails-app/controllers/com/privategram/DashboardController.groovy]: Unable to locate constructor with Class parameter for class org.codehaus.groovy.grails.commons.DefaultGrailsControllerClass  
 java.lang.RuntimeException: Unable to locate constructor with Class parameter for class org.codehaus.groovy.grails.commons.DefaultGrailsControllerClass  
      at java.lang.Thread.run(Thread.java:662)  
 Caused by: java.lang.reflect.InvocationTargetException  
      ... 1 more  
 Caused by: java.lang.NullPointerException  
      ... 1 more  
 [/privategram].[default] Servlet.service() for servlet [default] in context with path [/privategram] threw exception  
 java.lang.RuntimeException: java.lang.RuntimeException: Unable to locate constructor with Class parameter for class org.codehaus.groovy.grails.commons.DefaultGrailsControllerClass  
      at org.codehaus.groovy.grails.web.mapping.filter.UrlMappingsFilter.checkDevelopmentReloadingState(UrlMappingsFilter.java:298)  
      at org.codehaus.groovy.grails.web.mapping.filter.UrlMappingsFilter.doFilterInternal(UrlMappingsFilter.java:199)  
      at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76)  
      at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)  
      at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)  
      at org.codehaus.groovy.grails.web.sitemesh.GrailsPageFilter.obtainContent(GrailsPageFilter.java:200)  
      at org.codehaus.groovy.grails.web.sitemesh.GrailsPageFilter.doFilter(GrailsPageFilter.java:151)  
      at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)  
      at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)  
      at javax.servlet.FilterChain$doFilter.call(Unknown Source)  
      at org.grails.plugin.resource.DevModeSanityFilter.doFilter(DevModeSanityFilter.groovy:44)  
      at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)  
      at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)  
      at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:369)  
      at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.invoke(FilterSecurityInterceptor.java:109)  
      at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.doFilter(FilterSecurityInterceptor.java:83)  
      at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:381)  
      at org.springframework.security.web.access.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:97)  
      at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:381)  
      at org.springframework.security.web.authentication.AnonymousAuthenticationFilter.doFilter(AnonymousAuthenticationFilter.java:78)  
      at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:381)  
      at org.springframework.security.web.authentication.rememberme.RememberMeAuthenticationFilter.doFilter(RememberMeAuthenticationFilter.java:112)  
      at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:381)  
      at org.springframework.security.web.servletapi.SecurityContextHolderAwareRequestFilter.doFilter(SecurityContextHolderAwareRequestFilter.java:54)  
      at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:381)  
      at org.springframework.security.web.authentication.AbstractAuthenticationProcessingFilter.doFilter(AbstractAuthenticationProcessingFilter.java:187)  
      at org.codehaus.groovy.grails.plugins.springsecurity.RequestHolderAuthenticationFilter.doFilter(RequestHolderAuthenticationFilter.java:40)  
      at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:381)  
      at org.codehaus.groovy.grails.plugins.springsecurity.MutableLogoutFilter.doFilter(MutableLogoutFilter.java:79)  
      at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:381)  
      at org.springframework.security.web.context.SecurityContextPersistenceFilter.doFilter(SecurityContextPersistenceFilter.java:79)  
      at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:381)  
      at org.springframework.security.web.FilterChainProxy.doFilter(FilterChainProxy.java:168)  
      at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:346)  
      at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:259)  
      at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)  
      at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)  
      at org.codehaus.groovy.grails.web.servlet.mvc.GrailsWebRequestFilter.doFilterInternal(GrailsWebRequestFilter.java:69)  
      at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76)  
      at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)  
      at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)  
      at org.codehaus.groovy.grails.web.filters.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:69)  
      at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76)  
      at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)  
      at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)  
      at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:88)  
      at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76)  
      at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:346)  
      at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:259)  
      at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)  
      at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)  
      at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:225)  
      at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:169)  
      at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:168)  
      at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:98)  
      at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)  
      at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407)  
      at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:999)  
      at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:565)  
      at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:309)  
      at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)  
      at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)  
      at java.lang.Thread.run(Thread.java:662)  
 Caused by: java.lang.RuntimeException: Unable to locate constructor with Class parameter for class org.codehaus.groovy.grails.commons.DefaultGrailsControllerClass  
      ... 1 more  
 Caused by: java.lang.reflect.InvocationTargetException  
      ... 1 more  
 Caused by: java.lang.NullPointerException  
      ... 1 more  

I doubled checked my UrlMappings again and they seemed fine, so I was pretty certain it was something to do with the reloading, and sure enough, after restarting the app, everything was okay. I guess they didn't tell you that not everything is reloadable?