I still say it's ground!
Check the ground wires at each of those locations, not just the hot leads.
There is a ignition wire to the starter solenoid that if improperly connected WILL NOT START THE CAR! And it's a small wire, about 16 gauge. It's easy to hook it up the wrong way.
2009 ML350 (84K) - Family vehicle
2001 CLK430 Cabriolet (71K) - Wife's car
2005 BMW 645CI (124K) - My daily driver
2012 Mustang V6 (60K) - Daughter's car