IHOS104 going idle and spinning full speed during dvd playback

I just bought an Lite-On IHOS104 blu-ray drive for use with Windows Media Center. Unfortunately, the driver speed changes all the time when watching a retail DVD: Is starts out quiet, than after a couple of minutes goes idle, just to come back on again spinning with full speed. Needless so say, this is rather distracting.

Any ideas what might cause this? I’ve also tried PowerPVD 10 with the same disk and the drive works properly with that program. So this looks like a software issue, right?

Is there are way to prevent the drive from going idle during DVD playback? Maybe somekind of firmware hack?