"Cannot empty clipboard" - cut and paste problems

A user in our department regularly copies data from a non-Microsoft program
(Business Objects) to Excel 2003. By selecting "Copy All" in Business
Objects, she usually has no difficulty in copying and pasting the data to
Excel. However, at least once or twice a week the copy and paste function
stops working (the "Paste" is grayed out when she right clicks in Excel,and
CTRL V doesn't work either) and she has to reboot her computer, which is
obviously a frustration and waste of time. I looked at her computer today and
went to Edit Office Clipboard, but the error "Cannot empty clipboard" came
up. Closing Excel and/or Business Objects and restarting them doesn't help
either.

Thanks.