I have been having the same problem. I will try the suggested solution that was already posted. I pulled the text below straight from their website. Here is a direct link:
http://www.wsbtv.com/station/4012845/detail.html
WSB-DT Makes Required Change to Digital Encoder
POSTED: 4:59 am EST December 21, 2004
ATLANTA -- WSB-DT performed technical changes Monday to its digital encoder as part of an FCC requirement.
In order to receive WSB-DT's digital signal, viewers must force their set to go through an auto-rescan in order to recover and receive the signal.
Viewers should consult the directions for instructions on how to program the set to re-scan.