Try Heimdall one more time, but this time, grab one of the bootloader packages. It sounds like there's a mismatch between your bootloaders and your rom (e.g. froyo bootloaders and gb rom).
Before I flashed THS ICS i flashed GB bootloaders and now I'm trying to flash stock GB
I'm gonna reflash the GB bootloaders if this screws up like every other flash ive attempted my phones history...