This is really a wierd issue.
It doesn't quite fit black screen watching TV because:

A) I am still getting audio at the box.

B) I can watch that tuner on any other box, and then I can watch the next to last tuner at this box.

C) I can also playback any previously captured material at this machine.

Here is my configuration
Box - Tuner - Priority
MBE/FE - PVR-150 - Tuner 2
SBE1/FE - PVR-150 - Tuner 1
SBE2/FE - PVR-500/1 - Tuner 3
- PVR-500/2 - Tuner 4 - First Tuner selected in WatchTV mode

If I am at SBE2 and select Watch TV it goes through the motions, I get audio for the program but I never get the video.

If I am at SBE1 or the MBE I can select Watch TV and I get Audio and Video.

Now here is the quirk, I have selected Watch TV at either SBE1 or the MBE and they are working. Leave that running, Then I go back to SBE 2 select Watch TV and it brings up Tuner 3 or the first Tuner in that PVR 500 and everything plays fine on that SBE/FE.

I don't see anything in the log files for this issue and I rarely "watchTV" I know it worked before it got upgraded to R5F27.

Thoughts, anything I might start looking for?

I know all the parts work because I can simultaneously record 4 streams, or even watch that Tuner from another box, just not at this box via watchTV.

TIA.