Is your database split (back end with data tables, front end with forms, queries, etc.)? If not, it should be. I'd guess that splitting your database will solve the problem (or reduce crashes to an occasional instance).
Put the front end on the local computer, with the back end on a shared network drive.
Have you set up security? I'd do that, if you haven't already, to stop someone from inadvertantly damaging something.
Is your network stable - "Disk or Network error" sometimes means just that.
Look at your interface - do you have data entry or edit forms that stay open for long periods of time? I've seen crashes that happen when a partial record is entered, and left in limbo for a while.
Do you have a lot of data being entered or modified by a number of different users? If so, you may have a record locking issue. I've got one instance where I save the data to the local hard drive, then dump it to the network every few minutes.
That's what I can think of off the top of my head - I'm sure there are other possibilities.