Outlook Express 5.0 Addr Book App Error

I’m running Windows NT 4.0 with SP6. When attempting to edit or add any entries into my Outlook Express 5.0 Address Book I get an Application Error stating:
DirectDBNotifyWndProc: msimn.exe
“The instruction at 0x0ff3a731 referenced memory at 0x00000000 the memory could not be read.

Any suggestions????? Thanks.