IE 5.00 Generating Error Message!

I manage a network with less than 50 users which is running off a SBS 2000.
On five workstations every time the users want to access internet they get this error message.
“IEXPLORER has generated errors and will be closed by Windows. You will needto restart the program”. I suspect it is a bug in the software. What really should be causing this error message to appear?