In IntelliJ I get this weird error when I try to compile.
Cannot find annotation method \'cascade()\' in type \'javax.persistence.ManyToOne\': class file for
Isn't that similar to this SO question?
The solution there was to add all JBoss jar (which you did), but also all persistent-related libraries (like Hibernate)
See this JBoss project configuration for example:
alt text http://jdick.co.uk/blog/wp-content/uploads/2008/12/projectstructure1.jpg
In short, ejb3-persistence.jar
might not be the problem here, just a symptom of other elements missing.
Or, if it is the problem, it may be related to the fact that it is not deployed correctly (for the WebApp configuration).
had a similar problem ("cannot find class spring...DefaultResourceLoader even though it was in my maven dependencies) and no amount of tweaking of revalidating caches seemed to help. Blowing away my $HOME/.Idea* paths and (basically) starting from scratch fixed it for me. At least for now...