ChaoDependant installed Final days of testing, and doesn't everything all seem to go wrong at the end!
It turned out that when the high power LEDs are running, they drag the supply voltage down by about 0.2V. Which would normally be OK, but the Hall sensors are giving voltages in the mV range, so the changing supply voltage gives a bigger signal than the actual magnetic signal.
Damn.
We tried a bunch of things, mostly involving big capacitors, but nothing worked really well.
