SharePoint is blowing up with Unhandled exception - Rowan Prior

Good day,

I have a number of sites running on my WSS 3.0; with MS SQL 2005 Std;
installation that have been working just fine for the past three months...
but latley, if a user attempts to checkout a document or open a document in
read-only mode, IE crashes.

I am prompted if I want to debug the application using Visual Studio, and
this is the error I see:

Unhandled exception at 0x7c812a5b in iexplore.exe: 0xC06D007F: Procedure not
found.

This only started to happen a few days ago.  Nothing has changed ( to my
knowledge ), and it doesn't happen on all documents.

Any suggestins?