To me, this is access' greatest flaw... It's not at all that stable when used in the wrong way.
Multi-user environments are always dangerous. When the database runs on a non-windows server, you're guaranteed to run into trouble too.
Luckaly you can (almost) always save your database from destruction. 'Repair and Compact' works like a charm. If that doesn't work, you'll be able to fine some tools to extract your data if the database appears to be a total loss.
I don't really know why this happens, but I'm running most of my databases with an Access-frontend and I store my data on a MS-SQL Server database. Quite a costly sollution, but hey, the company pays ;-) Since then, I never ever crashed again! (Oh-oh, not sure I should have said this out loud! ;-)
Seth