Is your hd box plugged into your TV via HDMI?
Another possibility can be simply a bad syncro between your TV and receiver if the problem becomes recurring. In those cases you need to shut everything down, unplug your receiver from the wall, unplug the HDMI cable, and plug your power cable back in. Wait for the boot THEN plug the HDMI cable back in (once you see the time your receiver is booted)
It happens more often with boxes that are left on during the night, but it could happen with any box that is plugged via HDMI, its one of these boxes failings.