Are you sure you have a GSA-5120D, A303 sounds more like a GSA-5160D?
It might be feasible to back flash, not sure if LG's flashers will permit this, you'd have to try to find out.
Shouldn't need drivers, should be a standard mass storage device. Drivers would relate to USB or IEEE-1394 controllers on the PC itself.
Problems could relate to the IEEE-1394 implementation/drivers. Also check that the power is provided to the unit, and that it is not using bus power (ie drawing from the 1394 cable). The problems described do not appear to be firmware related, nor be resolvable with firmware.
Try using the USB 2.0 connectivity, better suited to ATAPI peripherals.