Weird.
Check Menu >> Settings >> Preferences >> Time >> Power On Timer and Menu >> Settings >> Preferences >> Time >> Power Off Timer. Check Guide >> Schedule (yellow) and scan down the list looking for entries which correlate.
Do you have custom firmware installed? Use the WebIF Scheduled Events browser to check the schedule, as it shows all timer events not just recordings/reminders.
As a last resort, run Menu >> Settings >> Installation >> Factory Default. This will wipe all our settings back to out-of-the-box, requiring the tuning to be set up again and your recording schedule to be reprogrammed, but won't delete your existing recordings.