I tried jBPM3.2.6sp1 with JBossAS4.2.3GA and configured correctly in Eclipse.
I think there is something different between jBPM4.2 and 3.2.6 installation, any idea?
jBPM 4 is entirely different from jBPM 3 and an upgrade from a 3.x version to another 3.x version is something completely different from an upgrade from 3.x to 4. There are some posts in this forum discussing switching from 3.x to jBPM 4 and the potential issues you might face, just search for migration etc.. You might also want want to read up on the new features in jBPM 4. A good starting point might be this article from Joram Barrez. In essence: "jBPM4 can be best described as the result of smashing jBPM3 in a million pieces, carefully selecting the superb bits, putting them together with completely new or rewritten components by using the newest and fanciest glue available".
Hope this helps,