Lockup

With both 8.3 and 9.1 I'm experiencing occasional lockups on my S3.

What I see is that the s3 becomes unresponsive to both remote and faceplate buttons.

When I press any key (either in the remote or in the faceplate) I hear a sound from tivo (it seems like an error beep), but nothing else happens.

Often Tivo is recording at that time, and the recording seems fine.

The only way to regain control is to reboot the unit.

Any ideas on what may cause it -- I've thought of the possibility of my young kids pressing random key combinations on the remote to cause the lockup.

What I'm interested in is how to unlock it without rebooting (because the reboot makes me lose several minutes of the recording in progress).

Thanks.