I've been trying to help figure out his issue for a while now. I kept assuming it was a redirect issue with XenPorta, which I had once myself (conflicting with another add-on).
Was also worried that something "unknown" had happen during the import from vBulletin to XenForo. He had a few add-ons install before the import (already started community) and there is always that low risk of some unknown thing popping up.
Thankfully all is now seemingly running smoothly. Thanks Mr. Goodie2Shoes