It must be a configuration in the JBoss 5.X server that causes it.
Not sure what causes it, but I'm guessing this is a classloader problem. Best bet is to google this - I deploy as an EAR and don't encounter this issue.
On JBoss 5.1 it's even stranger - it doesn't throw any errors on startup but just aborts at some point and keeps trying to reload
Do you mean that the war keeps trying to redploy? This is a know issue with Seam 2.2 and Jboss 5.1 that causes continuous redeployment. Although I can't find the JIRA ref right now, the fix is available here.
Hope that helps, Pete.