I bought my LN32A450, set it up and had no problems for over a month. Then the Olympics started, and the HD robot effect kicked in just as described - every 5 to 10 minutes, lasted for a few seconds, then self corrected after a very brief break in the sound. BTW I am on Comcast with a direct cable connection, and I have a Pioneer HDTV that has never had this problem.
After a visit by Comcast to check the signal, which was just fine, I started searching on-line for a solution. I found the CNET Samsung forum where many others were reporting the same problem. Anyway, to make a long story a little shorter, I upgraded my firmware to version 1013, and the problem went away for about 2 weeks. So, I called Samsung's 800 number, they assigned a local repair shop to help me, and the main board was replaced, all within a week. Amazing service. So, it has now been 6 weeks, and my set still works perfectly. I checked, and the new board has the same old 1013 firmware, so the problem was not in the firmware.
Since I was prepared for the fact that I would have to redo all of my settings and channels, I took pictures of each of the many setup screens before the swap. Sure beat trying to write all of the settings down by hand.