Ed, try switching the SAP position when this occurs.
Occasionally my Fox channel on one of my DTVPalDVRs will play the second audio channel programming and not the main one. Perhaps yours is a similar issue.
Finally got to try that just now. Did it again while watching local Ch 5 news. English-only, nothing else to switch to. But what did bring back the audio was using channel Up and Down with the tuner. Changing channel up and back seems to reset the audio and it starts working.
The schedule data for channels 33-2 and 33-3 are swapped. Earlier I set a timer to record a program this evening on 33-2 and that is still good. But now the schedule shows that the program is on 33-3. Checking the content that is currently on shows that it is only the schedule that has swapped as the content is where it is supposed to be but doesn't match the schedule data. A quick check with other tuners shows that they are showing the correct data for these channels.
I noticed this problem a couple of days ago and performed a warm restart which fixed it. For a while.