Just to add to the support, I have been having this problem intermittently on my HR34 since about June. Initially it was on the local CW channel, then, thinking it was a dish alignment problem, I had the dish re-aligned, problem went away for a couple weeks and re-appeared on the NBC and occasionally the CBS locals. I have an open call for another dish alignment, but just found this thread.
I have not had the problem in the last week or two and keeping fingers DTV has solved the issue. If not, I believe the ultimate fix is to upgrade to the HR44 which does not appear to have this problem. The tech wanted to do this for me but I had about 50 hours of DVR programming on my HR34 that I would lose and decided to wait on this.