I'm amazed I didn't find this in a search of the lounge.
Running Bovey's Code Cleaner, Word2000 bombed out.
I deleted the infamous "data" in HKEY_CURRENT_USERSoftwareMicrosoftOffice9.0Word and the problem went away.
I suspect I have something in an application of mine that is somehow corrupting the Data item. Either that or frequent edits of my tool bars is generating corruption.