It seems to be an Eclipse
I've experienced the same error message, and after I closed Eclipse, deleted all old logs in workspace/.metadata, started Eclipse again it worked perfectly after a full rebuild.
Possibly the project needs a refresh and full rebuild. We use the refresh command and additionally
forcea complete and clean rebuild by forcing a complete compile by changing the compiler setting to another java version (from java 6 to 1.3) generates a incredible number of errors, but after switching back to java 6 everything works fine.
Small additional advice: I don't know if you've assembled the Eclipse environment yourself, but if your employer allows you; spend the money on purchasing a license for the JBOSS developent environment. We've spent numerous days to get all the plug-ins working together which cost absolutely a lot more than $ 99,-