Win2000, TAPI, Telephony & SVCHOST.exe

We’re Win2000 newbies (still waiting on that training!). We have a remote client with Win2000 and our Remote Groupwise email through a DUN setup for a local ISP. He’s getting a “Program Error, SVCHOST.exe has generated error and will be closed by Windows. You will need to restart the program”. We’ve tweaked and tweaked, and finally reformatted and started over out of frustration. But now the clean, patched (SP1) workstation is exhibiting the very same error when we try to setup the Dial-Up Networking for his ISP, alongside the Groupwise Remote client. Clues? Hints? RTFM suggestions?