Earlier this morning I had major "issues" with modules.
My web module couldn't see my EJBs, so without thinking I added the .jar I
was building as a library, and attached the source ( from the module ) to
it. This worked "kinda", but I started noticing really odd behaviour,
with classes missing from lookups etc. This would seem to be due to the
.jar getting out of sync with the source, and IDEA getting confused.
I eventually pulled that out, and discovered the dependencies tab on the
module definitions, where one can say "the web module depends on the
ejbs", which enables proper lookup and syntax error checking.
So - check those deps :)