Paste is grayed out between workbooks
 

Hi - I've got a couple of people who can copy and paste in the same workbook
just fine, but when they copy from one workbook and try to paste in a new
workbook, the paste option is grayed out. Ctrl+V does not work either.

This happens in all workbooks. It does not matter if it has links, came
from a client, or is brand new.

The only way to paste is to display the clipboard and paste it from there.
This is a temporary workaround, but annoying.

I've rebooted, repaired Office, checked for Viruses with MacAfee and run
Spyware doctor.

I can't find a solution online. Can someone here help?

Thank you.