Well, here's a couple of things you could try. First, get the latest MDSC and Jet DB components for the server (if you can do this for the clients, that would be recommended as well) as these dictate the management of data control in the OS. You can get these at www.microsoft.com/data. Next, you could check out this article:
 
http://support.microsoft.com/default.aspx?scid=KB;EN-US;Q296264&
 
I had a similar issue before with a COBOL-based (ick) application, and adjusting those keys fixed it. For some reason, several workstations would lay claim to the same files/db at the same time and not release, and this addresses that behavior.

Or just move it to PostgreSQL or MySQL and be done with it for free. MS SQL Server would probably be much easier to use and a lot easier to import the data into (along with link the Access front-end to), but it does cost a bit of money.

no chance of converting/upgrading, were getting stumped with the "its worked since 1994" line from him
 
seems ok now, problem may be down to a faulty machine crashing it out (typical) however thanks all for the mega helpful advice, im going to look into sql myself so may check the tips
 
cheers