PC Lockup when receiving email

Whenever the user receives an email through Pegasus Mail the PC locks up to the point of rebooting, the user has only Pegasus and Lotus 123 open. Why is this occuring?

The PC is a Compaq EP Celeron 500, 128MB RAM, 3com NIC, Creative CD-ROM.
The email program is Pegasus Mail 3.01b, other software on the box is Win 95, Office97, Lotus SmartSuite 9.5, WordPerfect, Access 2.0, and Proxy. And we are running Novell Netware 3.0.

I have tried reinstalling Pegasus, applying updated drivers for Pegasus, reinstalling Lotus SmartSuite, replacing the entire PC, deleting and recreating the email account on Novell. There are many other users with this same basic setup and no one else is having this problem. HELP!