That's odd, in my IPB table (running 2.0.4, the current codeset), the data stored in avatar_location is all in the format av-[id].gif/jpg for uploaded images.
Are you sure you're running an unhacked version of IPB2?
In reviewpost/forums/ib2.php, try this change:
Content visible to verified customers only.
(lines 228-236 ish)
The addition is "if ($avatar_type=="upload" ) $avatar_location = str_replace ( "upload:", "", $avatar_location);" as a first statement.