I have a Lite-On DVD +/- rw and haven't had any problems with it since i bought it (about 8 months ago) now all of a sudden it wont recognise some disks that are put it in. I first happened with a game that was on a DVD and i just put it down to a bad disk. It then happened again the following week with a game on a cd. In between these times it has read numerous DVDs and cds.
FW fittings get loose rather quickly--do you have a new cable you could try? If your'e handy (and the power's OFF) take a small tweezer and GENTLY bend the contacts in so that they have maximum connection. You might also see if a firmware update is available, I've used LACie in the past (and I don't have a LaCie drive). Basically you just need to match the chip on the board Oxford 911 or 912 or initio something. Do be carefare as this flashes your rom to the new version, and if you get the wrong one you'll have to do it again. Oh, and if you flash, revmove the drives first.
good luck
archinaut