Blank screen while accessing an mdb file

Hello.

One of my users is experiencing a problem while accessing a Microsoft Access 2000 database.

The problem is random and it happens from time to time.

The PC is a Pentium III 600 Mhz with 128MB of RAM.

While the user moves from record to record suddently the screen gets blank and the mouse freezes.

The user is forced to reset the computer in order to to get back to work.

Is this a memory or a VGA problem that causes this problem? Do I have to upgrade the memory?

Any ideas?

Thank you in advance.