Has this recently started? Do you have a DTA box or any other box hooked up to the affected TV?
I have the same problem with other stations in my area and it didn't start until I hooked up the DTA boxes. For me it has been going on since January and they have yet to resolve it. If I take the box off, they are all fine.
The only thing I can suggest at the moment is check to see if you can adjust screen size on your TV. If that doesn't work or your TV is unable to adjust the screen size, check to see if other channels are affected. For me, it's PBS, ABC, NBC, ESPN, ESPN 2, Headline News to name a few. The easiest channel to check is ESPN or ESPN2. See if the N or 2 is cut off.
I would then call Comcast number on your bill to see if they've been getting other calls in about it.