Take a look at the Virtual Dub filter DeLogo. It's a bit of a bear to get set up properly, but the results are pretty good for static titles. I'm not sure how well it would work if you've got a constantly changing number like timecode.
The filter averages surrounding pixels, based on an image mask you create. It leaves a little blurring (kind of like an airbrush look), but it's hardly noticeable on a moving image. You're looking at some pretty hefty render times, too.
Can you just crop the image to remove the offending title? This would be much easier.