Silly suggestion... because I don't really know... but are you using an older version of Access than the version that created the mdb files?
Secondly, and just an observation... I would never let my databases get to 1 gig in the first place... your buddy should compact more often.
Finally, there are a number of suggestions for corrupt databases in this forum... including opening a new db and trying to import components, etc. Suggest you search through existing posts.