Paul,
Based on the referenced thread, there are two file-server-custom.xml files. One in the standard "extension" directory that should be there and one that appears accidentally (maybe intentionally) bundled into the aldresco.war file. Actually there may be three if your jboss explodes war files upon deployment.
You can cheat and just edit "file-servers.xml" file, though most will say not to do that (by the time you upgrade you will have forgotten that you made that change, plus a re-deploy of the war could over-write the file).
The second is removing the offending file entirely. The exact jar commands maybe a bit off as i'm going by memory.
1. Find "alfresco.war".
2a. On unix extract the archive with "jar -xvf alfresco.war" this assumes you have your path correctly set to run the jar command.
2b. On windows, open the archive the same way via a command prompt or use an archive tool like 7-zip (my preference when I have to windows).
3. Find the file "file-server-custom.xml" and delete it.
4a. On unix re-create the alfresco.war file with "jar -cvf alfresco.war alfresco"
4b. On windows if using jar see step 4a otherwise just close the archive in 7-zip and it will prompt then save the updated version.
5. Restart jboss.
The offending path will be "alfresco\WEB-INF\classes\alfresco\extension\file-server-custom.xml" in the webapp root of jboss.
That should do the trick.
