Premature disc finish (WinXP SP1)

Well, I'm stumped. I just reformatted and installed WinXP which had SP1 already integrated. Everything seemed to be working fine until I tried to burn a DVD tonite. RecordNow (with latest PxEngine) stops at about 25%, ejects the disc and states that the operation has completed successfully. Clearly it hasn't. I havn't changed anything from when I was running just WinXP w/o the SP. I also noticed that while the burn light is lit on the drive, there is zero HDD activity. Some type of communication error? Specifically, I am burning the VIDEO_TS and AUDIO_TS folders back to Apple media. I tried changing the drive into PIO only mode (which I didn't need to do previously) and that also ended in the same fate. I disabled Windows' integrated CD recording as well as unchecking the "Enable CD Recording on this Drive" under properties on the A03, as suggested in another post. I'm running out of ideas. Any suggestions appreciated.

Just a quick update. I installed Nero v5.5.9.9 to try for sh

i dunno........i've had bad exp with recordmax........just stick with nero from now...

The disc created with Nero plays fine in 4 out of the 5 players I tried it on. The same media burned with RecordNow went 5 for 5. Think I'm just going to reformat and try again. I don't want half-@ss discs.