Turn the key starter clicks and then all power is lost.

2001 Jeep Cherokee Sport. We're
already checked and replaced all
connections including battery
terminals , new battery, alternator,
starter and ignition switch. Still has
the same problem. Checked the leads
from battery to starter, alternator,
starter and ignition switch. Checked
all their grounds. The lead from
ignition switch to starter has constant
power as it should until turn key to
start. Then then the bendix gear
comes out hits the fly wheel and all
power is lost for about 5 minutes.
Then we get power back. Hand
cranked engine to make sure it wasn't
seized. The engine is fine. Aside from
replacing every wiring harness and
500 ft of wire...what else could it be.
We are so stumped. Any wiring
electronic gurus in here?