update failure

Hi, I’ve been trying to update Comodo antivirus on my Vista lappie, in response to an update available prompt - but it seems to be stuck in a loop, as it has been updating for six hours, and is still going! When I put the cursor onto the toolbar whick shows download in progress, it is indicating copying cfpupdat.exe file.
CPU usage is 100%, and I can hear the mobo ‘chuckling’ away, but there is no other indication of anything happening. The pc is still functioning, albeit slowly.
ny advice would be appreciated.

Does rebooting help here?