I have wireless mouse. Also a wired keyboard i keep attached for when i need access b4 pc is completely booted. I had same prob only rebooting did not help.

Found out the keyboard had tipped over (had it on it's side to save space) and one of the F keys (or some key) was depressed. Moved the keyboard and all worked ok. So it could also be a stuck key. Did not have a repeat or 'buffer full' beeping.

Hmmmmmmmmmmmmm.

just some FYI.