I am in a similar situation and was wondering if anyone on this thread could help me out. I recently upgraded my sister's iphone 3G from 4.1 to 4.2.1 and am stuck with 05.15.04-5.9_M3S2 baseband and bootloader.
However, before I upgraded from 4.1 to 4.2.1, I saved the SHSH using TinyUmbrella. Does this help me at all? Can I downgrade the firmware to 4.1 and restore the original baseband with the SHSH I saved?
Thanks!