This is the issue - Dish hasn't gone to full time HD RSN's...they have gone to 2/3rds time HD RSN's. Once Dish moved the RSN's to be in HD more than just the game, there is a hard cutoff on all the main RSN's HD feeds at 3am ET, 2am CT, 1am MT, midnight PT. The HD RSN goes "Off-Air" and comes back on at 11am ET, 10am CT, 9am MT, 8am PT. The one positive thing that was nice about the old system when it was game-time only HD was that the game would stay on as long as it was live, even if it went past the off air time slots.
So my guess is right before you went to bed, that message was due to the hard cut-off of the HD channel.
I have written to Dish about this and I have gotten two responses: 1) they re-use the bandwidth from the HD RSN's for other things during the overnight hours when the paid programming is on and 2) they are only contracted to have the channels in HD 16 hours per day, which is why they have to have the hard cut off.
This has happened more than once since Dish has moved to this 2/3rds time HD RSN's. When the Cubs or Sox play a game on the west coast that goes longer than the 4 hours 50 minutes window, the game gets cutoff and I have to turn to the SD channel. I don't stay up for west coast games usually, but if I want to record it I have to record on the SD channel to ensure the complete game.