Is the termination set to auto in the adaptec scsi bios? Are both mounted internally? Do you have terminators on the cables or are you using the drive termination? What termination on the drives were you using, just the plain terminator enabled, or was it terminator power to bus enabled, or terminator power to drive? Do you have the latest bios for the card installed, some of the newer ones give better error messages.
Though they are different channel's, on that card, I've had one channel's termination, screw the other channel up.
Generally, I use active terminators on the end of all cables and turn the terminators and anything related to terminating, off on all drives.