Are all the users accessing the same hosted files, but only one is experiencing crashes?
Try deleting preferences on that one machine.
Look for any patterns as to what that user is doing just before the crash--maybe there's a clue there as they may be accessing a problem record, layout or script that your other users are not.
If they use a local front end file to connect to a shared, hosted back end, replace the front end file with a copy from one of the other machines where crashes are not happening.
Take last night's back up of your file and run a recover on it to see if any problems are reported. If any are, replace your damaged file that is in use with an undamaged backup. (A copy that recovers "cleanly")