Ah ok ... I think I've figured it out.
Your bridge IS actually grounded - it shares a ground with the bridge pickup. This is actually not uncommon in a Tele. Instead of a seperate wire that links the bridge to ground, there's a wire from the bridge plate to the pickup's baseplate, which is also connected to the pickup's ground lead (the baseplate of a tele bridge pup is usually grounded). When you flip the phase of the bridge pup, you're also lifting the ground off the bridge itself, thus cutting the ground path through the strings to your hands, thus adding the noise.
Yay me! I am so smrt!
You have two options:
Hard option: Take your bridge off, disconnect the bridge ground from the pickup, and run a seperate ground lead from the bridge plate to ground.
Easy option: Instead of wiring the bridge pickup for phase reversal, wire the neck pickup. It will produce the same effect and you won't have the annoying ground lift problem.
Cool?