Google the following:
Run-time error '91: Object variable or With block variable not set
I don't know if this will help, but I trust Google more than, well...
There are quite a few "ideas" there from giving permissions to certain files to using Registry Cleaners. I guess it can't hurt much to try a reg cleaner even if you aren't one who likes them. I would be a bit skeptical about the programs which are touted to fix the error. The problem is, like many error messages and especially the ones pertaining to "variables" rather vague. They can mean more to programmers.
One of the things people clamor for with Microsoft is better error messages with less Greek.
