Maybe it's somehow related with another "error". If I create a new JBoss AOP Launch configuration (with the "Run..." menu), the plugin says right at the top:
[Source]: Launch configuration does not support source lookup
And in the source-tab, I can't add sources... Nothing happens if I click on the "Add" button...
Thanks for your answer. 1.5M2 (AOP Developer) works better indead.
Unfortunately, I'm still having problems with compiling my AOP application in eclipse. I'm going to open new threads on these.