I stumbled on this site because of the servo mod for continuous rotation. Best I have seen.
When you troubleshoot a program you need to see what is happening with your variables. At the moment you don't know where the problem is, but if you knew what values were coming from the photocells after the A to D, you could see if they were behaving. Similarly you could see what the values were going to the servo.
Typically you would sprinkle test points (and probably slow down the loop) and track what is going on. That is fairly simple to do with an Arduino when it is tethered to a computer. You open a serial connection through the USB and watch the data being printed out.
That is exactly what I do when I am debugging a program. Debugging by guessing, is a lot like fixing a car by guessing and is why all cars now have diagnostics where you can read the various engine settings and codes.
I would be willing to contribute to code for an Arduino version of the $50 robot, I won't be building one though.
I'll try to see if I can Debug based on what you said. I used to arduino to check the light and dark values of the photocells, and i got a good response. Ill see if i can find anything else Also if possible, you can contribute your code just incase.. Much appreciated.