I have the same unit.It ejects of its own accord once inserted it wont read disks and definitely wont record onto a dvd.It doesnt even see blank dvds anymore.
Looking on ebay there are a few of this model that all have the same problem.I can't give you an answer, but I would look at replacing the dvd.Its just like a pc connection. Data cable and power cable.Its 4 speed apparently.
It prolly needs the 'gain' turning up on the laser as they all lose their power over time.Thing is mine, prolly like most has had the dvd reading/burning side of things used only occasionally.
Roy
November 2008