I also have this issue, using JBoss AS6 and Seam 3.0.0.final, only instead of WARs in my EARs, I have JARs.
They have the same specification in their beans.xml though, and I'm getting the same issue.
Did you determine the cause or find a workaround?
We found that the seam interceptor can only be defined once (i.e. not in multiple deployment untis like jars). So we only have the seam transaction interceptor as well as our own interceptors in one beans.xml only, and that beans.xml is included in One jar inside ear's lib. That seems solve the
This might be because of the fact that jboss 5 and 6 uses different classloaders for ear and war?
But since you don't have war, I don't know the cause for your problem.
Now we are moving to jboss 7 and this problem might be gone or might be worse. We will see.