Been having this problem for almost a year now. We got a new Samsung tv about the same time that the LNB was upgraded. Two receiver replacements and no solution. The pvr will randomly reboot itself during recordings and/or we will turn the tv on and the black reboot option screen will be there for user input. Our current receiver has been in place for 3 months and has over 1000 reboots!!
These are the things that have been tried so far with no change…

• plug the receiver directly into the wall
• replace the plug outlet
• replace the hdmi cable
• do a soft reboot of receiver
• move the receiver to an older Samsung tv and everything is fine
• plug the satellite hdmi into different inputs (1,2,3 & 4)

Not getting rid of the tv anytime soon, but this issue makes the pvr capability almost useless.