[DanL]

Yes, start with tracking.zip

If your setup is fine, tracking.zip should make your servos go from left to right constantly until they catch the light. If they aren't moving after you load tracking.zip, then...

1. Check your wiring.
1a. Make sure the proper pins of the receiver are connected to the proper pins of the pwm wire (check the usfirst.org pdf)
1b. Check to make sure each of the receivers are plugged in to the correct Digi-input. If memory serves me right, IR_1 -> int01, IR_2 -> int02 IR_3 -> int04 IR_4 -> int05 (where IR_1 is left on left servo) - note the skipping of int03
1c. Check to make sure the servos are plugged in to the correct PWM-out (check the code)
1d. Do you have the backup battery charged and hooked up? The servos don't run without it.

2. Troubleshoot the receivers
2a. Turn the beacon off. Do the servos move then? If no, the problem is with your wiring. If yes, the problem lies with the setup of the receivers
2b. Check for reflections
2c. Bring your beacon down to 2 or 1 emitter LED
2d. Ambient light (see Kevin's faq)
2e. Receivers 'shotgunned' enough?

That should be enough to get you started. The purpose of the tracking code is to get your setup working - if the tracking code doesn't work, go back and refine your physical setup. When you get that to work, go to navigate.zip. I personally found that testing the nav code on blocks was a waste of time... you need to have the robot moving on the ground to have the code work.