If you and your friend have done everything you say (not doubting just saying) and you checked your ground its time to start bypassing stuff.
Pull your battery and get some wire (10awg) and make a new ground for testing purposes.
Do the same for power (add an inline fuse, use whatever the smallest fuse in the system is) and start bypassing things like the rectifier, ignition switch, etc...

Im thinking a bad cable/wire. Something thats deteriorated or got a break in it.

SOLD: 07 Black BA, 39mm FCRs, TPUSA stage 1 head, TPUSA 813 cams, TPUSA 10.8:1 pistons, TTP #3 igniter, Specialty Spares Long Cannons, Tsukayu Hard Bags. 82HP/55tq NEW: 19 Goldwing Tour DCT