MS Word 2000 document fails to open

Anyone out there with the knowledge? Typically users are users they never admit what they do! So here’s the problem:

When opening any MS Word file below 100Kb in a Windows NT 4.0 is fine, loads very fast indeed but when the file gets any larger than that dear “Dr. Watson” comes out. Here is the error code:

Error ID: 4097
Bla bla bla c0000005
Address: 308c33e0 (MsoFAllocMemCore)

What happened? Right now the only solution is to format the NT and rebuild everything again. This one does it fine (cheap way to runaway) but the problem keeps coming back. Please help… anyone out there…