Optical mouse?  Not likely to have the problem I had, but anyway...

Some of the fibre wires in the mouse cable broke until there were only
one, or two, or maybe none, making a connection.

Symptom was *exactly* like yours.  Work awhile then mouse would hang.
sometimes ctrl-alt-del worked, sometimes not.  Kept at this for around
three months until the break was so severe, problem was no longer
intermittent but very constant by simply moving the cable.

             - Robert -

The mouse "not working" is usually because the video has stopped
repainting -- because the system has "hung".

Many, many things can contribute to this effect, but the first thing to
check is for malware.
See my article at http://www.grystmill.com/security.htm

General gunk can also lead to this problem.
See my article at http://www.grystmill.com/articles/cleanboot.htm

That last article will introduce you to MSCONFIG, which can be used to
trouble-shoot this kind of thing, though with your problem taking an hour or
two to kick in, it may take days or weeks to finally narrow it down. First
thing to do on this account is to show us the list of Startup items. You do
this by running MSINFO32 from the Start\Run box. Expand Software
Environment, click on Startup Programs. Click into the right-hand pane,
anywhere, then press Ctrl-A, then Ctrl-C. Open a reply here and use Ctrl-V
to paste in the data.

Note: If you already have items disabled in MSCONFIG, you want to write down
what they are, then enable a Normal startup, click OK, but DO NOT restart.
Then do the MSINFO32 thing, then go back to MSCONFIG and re-disable the
items that were previously disabled. You don't have to reboot when prompted
then, either. Also provide a list of those disabled items along with the
MSINFO32 info.

Thanks for the info -- I'm using old type roller ball mouse and haven't had
the problem again. I guess in need a new optical mouse.