If you are getting this error when trying to start a Grails Project in Intellij:
Error starting Grails: com/springsource/loaded/ri/ReflectiveInterceptor
try deleting the ./.slcache folder at the top level of your project:
projectname/.slcache
This problem came when I was trying to update an app to a newer version of Grails. The above solved the problem for me.