Idvd3 Burn Error



I have an iMac 1Ghz with a Pioneer DVD-RW DVR-105. When I try to burn a DVD using iDVD3 the burn process takes an unusually long time and finally an error dialog appears asking for a new DVD-R. The first time this happened, I was burning to a DVD-RW (which was wrecked - I can't even erase it with DiskUtility), but the second time I was burning to a DVD-R (8x).

I tested the DVD-R afterwards in both the computer and a DVD player and it appears to be working fine. Does this mean my burner has something wrong with it? I am a bit suspicious of burning any more discs in case they get wrecked or have missing files. Thanks!