Hey Duckster and Rongway,
I'm not sold on serrated edges anyway - they rip and tear. (Just try one on a good steak)
As far as sharpening a processor blade goes, I use a Nicholson (fine) flat file placing the processor's blade on the edge of a wooden bench. Do not file the bottom side of the blades. Hold the file at a 22-1/2° angle to the blade and simply remove the burr and sharpen the blade by filing one direction only - into the edge... not away from it. . If you do it correctly, it will shave hair from your arm. It will also eventually remove the serrations, but it's no big loss.
Oh,... how do you find a 22-1/2 degree angle? Fold a piece of paper in half and you have 180° right? Fold it over again and you have a right angle (90° angle). Fold it in half again and you'll have a 45° angle. One more fold will produce a perfect 22-1/2 degree angle - recommended by most cutlery manufacturers.
Best Wishes,
Chuckwagon