All of a sudden, Excel 2007 has learned a new and unwanted trick - when I select a cell or range of cells and enter ctrl+C (or Copy from the Clipboard group), the cell outline flashes for an instant but then reverts to its normal display. When I paste into another cell, it acts as if I have selected Paste Value, not Paste. When I click on the Paste options in the Clipboard group, the drop down shows only Paste, Paste Special, and Paste as Picture - all other options are greyed out. When I select Paste Special, the only options presented are Text and Unicode text. I have searched but cannot find an Excel configuration option or an MS Office Clipboard option that might produce this behavior.
I have MS Office 2003 as well as 2007 installed on this machine, and Excel 2003 now exhibits the same behavior. It persists after a reboot.
Please help me restore normal functioning.