Ah! I didn't realise that. Might explain some of my problems.
Can OPU problems be "partial" or is it usually "all or nothing"? My DVD reading/writing ability, which I formerly thought was completely gone, has after some experimentation proven to be very poor but still possible under certain circumstances.
If I put a recorded DVD-R in the drive and leave it to whirr for maybe 2-5 minutes eventually it might recognise the disc about 50% of the time. After that I can easily read it, transfer files etc. It isn't disc specific though - sometimes the same disc will never be recognised, other times it can eventually be "seen".
My drive (SOSW 852S) still completely refuses to recognise any blank DVD media no matter how long I leave it.