I did, and I double and triple checked all the wiring.

It turns out the GFCI outlet was the cause of all the problems. Someone
on the alt.construction.building group pointed this out. I'll quote
him:

If you use a regular receptacle, everything should work fine with your
circuit. For the GFCI to work properly, the current in its hot and
neutral loads must be equal, and this is impossible to insure when the
lights have a separate parallel power source. So if you want GFCI
protection, you need to put it in before any of the switches.

Cheers, Wayne

Thanks for all the input guys!

Adam