Now personally my choice observation here is maybe you have a hack conflict.
I have a totally clean
vb and vbgallery install no other hacks or products installed. Clean
vb code in every way. Now if I register a user in
vb the userid is entered in the vbgallery users table. Things appear to work just fine.
Therefore as I believe I have posted before the first order of business is to uncheck all other plugins and leave
vb and vbgallery as default code and test.