It can't be that hard to fix.

Disabling/revoking the profile URL modification will fix that aspect of it.

As for the avatar, just make sure it uses the same write/read function as the signature, location, join date and post count fields, which I assume are user number based, rather than username based, which seems to be avatar specific.

Of course, you shouldn't have to do this yourself when you're paying for vBulletin. But still, I know you're pretty knowledgeable administrators here (you still see some idiots running forums) and wouldn't have trouble doing this.

Just a thought.

By the way, I'm the one who referred .Mark/MarkNET here, which accounts for my high interest and contribution in this thread.