would need more info.. as you are in forum: general discussion..
is your gallery, vBGallery or Photopost Pro?
what version? vbgallery 2.x or 3.x?
are you running vbulletin 3 or 4?
I'm asking because in vbgallery, if you upgraded from beta 1 to a newer version some usergroup permissions changed...
If you have changed nothing.. maybe your provider upgraded from php 5.x to 5.3x.. in that case some things could have changed..