Thanks for the response (as usual).
I believe it's narrowed to just prime time CW shows and only on the HD version of the channel (781). The SD channel (7) works just fine. The local network affiliate broadcasts all work just fine. Last night it was black from 8-10pm and right at 10, the local WWMT news broadcast flipped right on.
This afternoon, at 5pm I was able to watch AmericanDad on channel 781 in full HD w/o any trouble. At 8pm and all the way through 10pm, both Oh Sit! and The Next went blackout and then the channel came back on at 10 for the local news broadcast.
This happened on both my Charter HD box and my CableCARD DVR with Tuning Adapter.
Also-- last week, I do know that it worked as the wife watched one of the prime time CW shows (it was one of those girl shows CW likes so much, so I can't tell ya for sure what it was).