[Alan Anderson]

Are you using a Victor, or a Jaguar? Are you using the appropriately matching object in your code?

From what I've seen so far this year, Victors are more prone to asymmetric behavior because of their offset neutral point. The WPI library code does a good job of accommodating this, but any given Victor might not be exactly as the code expects. If you're using a Victor, try calibrating it before doing any more programming. Hold down the CAL button when applying power to it, send it "full forward" (+1), then "full backward" (-1), then "neutral" (0) signals, then release the button. Its LED should flicker green to let you know the calibration was successful.