A java error in a proxy file is hard to fix, since they are generated every time you deploy your app.
The error is usually caused by a Javasource folder from an older, deprecated module: in that case, try deleting all folders you find in the Javasource folder that do not correspond to a module in your project, either custom or marketplace. Then, go to App > Clean Deployment History and try again.
If the error persists, it is wise to try and isolate the conflict with a version control program, such as SVN, and fix the conflict from there.
Use tortoise svn to clear the merge conflicts