[Revan]

You have to check if this is happening to users newer than his userID.
I have a somewhat similar problem on my live board actually, it absolutely REFUSES to fetch the RPG Name of newer members.
Actually, now that I went to check this out for myself, this problem seems to have gone away on its own...
*ahem* anyways
You could do that userid check (with a modded showthread obviously), then if it does not happen, verify this by posting some with a temp account you create, and if this still is not slammed by the problem, merge the two into the new userid.
Hassle, but stuff like this is impossible to detect and remotely fix