I encountered the same problem and after some (serious) digging and debugging I found the problem in my case was that it was writing the byte order mark (bom) in front of each String because the method in class org.jacorb.orb.giop.CodeSet.Ucs2CodeSet.write_bom(boolean) always returns true.
I'm not sure why WebSphere doesn't like this as I think this how it's supposed to work (googled http://recode.progiciels-bpi.ca/manual/UCS_002d2.html), but still I got it working by modifying the method to return "false" instead. The class is located inside <jboss-as-7.1.0.Final root>/modules/org/jacorb/main/jacorb-2.3.1.jbossorg-1.jar.
Hope this helps,
Any idea if this issue is resolved in Jboss 7.1.1 Final?
I'm facing some problem right now whereby I have a Jboss War in Jboss 7 which need to remote connect ejbs in Websphere.
Please create jira issue for this