I assume there is nothing displayed on the front panel?
If there is I would try playing with the TV source to see if you can force a picture.
It may be that the unit was actually recording before the TV was switched on and the problem relates to a HDMI sync problem. Have you also tried turning the TV off into standby and turning on again?
The only other problem I can think of is a HDMI-CEC control problem – try disabling it on your TV (Search for HDMI-CEC and your TV brand to find out what they call it.)
If no luck, and especially as you say the problem is recent, I would suspect a defective unit (or power supply).