Well I installed a new GFCI as the very first receptical on a circuit (added a new line cable from the panel, and the old line now becomes the load coming out of the GFCI). My original questions and why I did that can be found in this thread:
It looks like I installed the GFCI properly - resetting it works and the light on it comes on. Everything downstream on the circuit works (recepticals, room lights, etc) EXCEPT for a hardwired hallway light. Turning that light on trips the GFCI. I can reset the GFCI fine after that, but it will trip again if the light is turned back on. The only unique things I can _see_ about that light is thats a 3-way.
Any suggestions? Probably not since thers very little information here. Ill need to troubleshoot this more tommorow.