Hello,
Based on the information you have given us, I would guess that this is a problem with your AVR setup or code, not the gyro. Can you simplify your system as much as possible, then post your entire code and a detailed description of the circuit and a picture if possible?
In particular, I recommend removing the gyro from the circuit and replacing it with resistor voltage dividers giving you approximately the voltages you expect. On the other hand, if take work as expected and you suspect that the gyro is the problem, you could remove the AVR from the circuit and look at the gyro outputs with a multimeter.
-Paul