The users in this thread and this BEA forum thread found out that running XFire under WebLogic can lead to some problems. The solution is to relocate the qname.jar file to the front of the classpath using the WebLogic startup script or using the MyEclipse Paths connector configuration screen to append the JAR to the classpath at the beginning.

Update: It seems that BEA acknowledges this workaround and says putting qname.jar earlier in the classpath is safe. They are also working on a patch.