msgsvr32

It could be a variety of things, depending on the exact error message. For example, the error message says, "msgsvr32 caused_______in_______. (Or something similar.)

Look at this link for an explanation on what msgsvr32 is, what it does, and some possible causes for the various errors.

http://www.geocities.com/Athens/Troy/6883/msgsrv32.html#Explorer%20Caused%20an%20Invalid%20Page%20Fault%20in

or

http://tinyurl.com/tpik

If nothing else, reinstall Win98 over itself. It'll keep most if not all of your settings (on mine it only changed folder settings) and it'll refresh your system files.

Also run a virus check beforehand.