A couple of ideas:
1) add a user field to the records in the temp table.
2) name the temp tables after the user
3) separate your front end .mdb(code, queries, reports, etc) from the back end (shared tables) and create the temp tables in each user's front end. Then use linked tables to tie the two together.
4) put the temp tables in a separate .mdb organized by one of the above methods.
3 and possibly 4 are probably your best bets. You'll want to account for the need for occasional db compaction wherever those temp tables end up too.