I didn't solve the problem, but I have a temporary solution.
Instructions (By now):
Lets imagine you did redsn0w tethered and then greenpois0n untethered RC5, you might realize gba doesn't work anymore. So if you still have redsn0w 0.9.6b4 open it, select the 4.2.1 firmware and then select ONLY "Just boot tethered right now". After following the instructions and entering DFU mode, your ipod/iphone will run being able to use gpsphone.
You won't lose greenpois0n's untethered after redsn0w, so if you restart your device it will work normally.
The problem is that every time you want to use gpsphone, you will have to do the redsn0w thing.
P.S.: I'm not sure this instructions will work for someone that never did redsn0w on his device, but if it works let me know
Cheers from Chile.