Some part of your deployment doesn't know about the new
method, probably because you haven't redeployed it.
Moreover sorry for my english, i'm italian.
I have the same problem, and i found that also if you redeploy the project, the error remain! The only way is to stop the JBoss and restart it. So is ok, but if you redeploy the project for whichever reason (also only to write a comment) the error come back!
I use JBoss 3.2.2RC4 and JBuilder9 with the Voyager OpenTool 2.6alpha.