Bug: ArcMap table window does not show attributes for joined personal geodatabase data
After joining a personal geodatabase table to a feature layer, attribute values in the joined table are blank or null.
One of the field names begins with a non-alphabetic character, such as Number or Underscore, or the field name contains a space.
_FIELD or 1FIELD or FIELD NAME
Make sure all field names begin with an alphabetic (a through z) character, and contain no spaces.