I wonder if the problems encountered by so many users of this new HDPVR box are attributable to overheating. As soon as I installed a small fan on my PVR, all problems (so far) have vanished. My HDD temperature reduced from a high point of 56C to an average of 32C. I know it may be difficult for most readers of this forum to try this, but a small, muffin style fan (12V, 2W) run from an a.c. adapter is my recommendation. You can try a small table fan as an experiment for a few days. If you're dissappear, it may be that your PVR was running too hot.
My fan is placed a few inches away from the right side of the PVR box. Worth a try, and if it works for others, I encourage feedback to this forum and to Motorola. 56C doesn't sound very hot, but there may be other devices inside which run even hotter, well over 60C, and therefore cooling the whole box is a long term benefit.