I had this same exact problem when my limit swithes were wired in series normally closed. No matter what I tried, the MACH program would say that a limit switch tripped for absolutly no reason. I tried everything to isolate the wires, ect.
I ended up wiring my limit switches in parallel normally open, not one problem since, and it doesn't make a diffrence if the limit switch cable is wrapped around the servo power cables...
Should fix your problem, exactly what's causing the problem I'm not sure, but that will fix your problem.
Michael