This may be a case where you need to restart the server after making a change or deployment. I found that there were times where either deploying or making a configuration change required a restart. See the reference guide Installation and operation of Weblogic for more details on it.
If that is not the case - could you provide some more details around this?
- Seam Version?
- Any of your own changes made?
- Other exceptions or errors?
- The reference guide provides more details - please verify your steps to that as well.