2 ideas might help
Check to see if you have something recorded that goes past the hour -- like to 10:01. If you do and you have 2 shows set to record at 10:00 there is your third recording.
If that is not the problem then. I would do a full reboot. Turn off the box and the TV. Unplug the box for about a minute and then plug it back in. It will take several minutes to reboot, it is done when the time comes back up. The you should be good to go.
I do this to my box 8300HD about every week or two and seem to have very few problems.