First post here for me; saw I may be able to shed some light on this. I usually stay away from posting & only read post to learn & see others views. But you sure seem to have what I have. My 3 week old 65737, purchased new from sixth has these problems one week after use (no Comcast box) channels started to become blank. I saw the Comcast bucket truck doing something out @ all the poles on my street the day my TV started resetting to channel 4. Freeze the picture & no controls would shut down, change the channel, volume etc. This was with digital channels only it seems, shutdown was without cooling down the bulb first. The next time I would turn it back on I would have a longer green flashing & sound would start before a picture would come up. The channel would always return to #4 (Comcast box here uses #4) no matter what channel i was on. Rescan, no change, all channels did show up in the rescan, hook up box, problem gone, disconnect problem re turned. No problems with any other input scores with or without the Comcast box. I had all versions of say channel 6, about 7 of them. Few channels w/box & no HD. there was HD channels w/out box.
Called Mit, I asked to hold for 3 mins. Had to repeat problem, asked to hold another 3 mins. I was told an update was on its way. I received the update today (8570xxx) on a thumb drive. I was trying to see what this update was before installing it when I found your post with what seems to be the same Comcast rebooting our TV's. Mit would not confirm or decline this to be true. Only that the TV would tune in the channels w/out shutting down any more with or without a box. I also asked if it is possible to punt you off like the old AOL. I was side step away from the question. I believe it is @ least possible to over load the signal & cause the TV to shut down using a built in safety like the over voltage protection circuits used in power supplies ect. Some free channels I believe they are not allowed to make extra charges to the consumer, local channels like 6 ABC HD, so they do this REBOOTING . Have your model & s/n ready & call them. The most they can say is no. hope this helps
I will post back later with the update results from the thumb drive.