Just a wild guest...

Could it be that the mouse is sticking? Try gently banging on the mouse keys
(including the wheel mouse if you have one)--or even swapping the mouse
(temporarily???).

Bugged by Excel? wrote:

Intermittent problem with Excel deciding to select a group or "array" of
cells and locking the array on the last cell in use. All program
functionality is gone and system must be re-booted to correct.

--

Dave Peterson