If after several reboots it does not recover you will have no choice.
What I have found with this receiver is that after several blind scans in a row it gets corrupted. My guess is the Blind scan app has a very bad memory leak. Also since it is is saving as it is going a simple reboot does not clear it.
If after several reboots it does not recover you will have to hold the front panel button in while applying power. Continue to hold until you are presented with a menu.
From there you can try to wipe the cache and such to see if that fixes it. If not you will have to repeat and wipe everything. Then use your most recent backup to restore, everything like it was at that time.
I have found if I am going to do a lot of blind scanning to back up every third or forth scan. Most of the time also, if I reboot the box every third or fourth scan I am usually fine. Every few months though I have to reset and recover.
If I don't blind scan I can go forever and no issues.
It is a sad truth from a great receiver. Since this receiver is no longer supported with new firmware, one has to deal with it, if they want to use it.