Since Defraggler was running exceedingly slowly on my machine (>20 hours and only 15-20% defragged on a simple 250 Gb SATA drive), tried running in debug mode. Let it run for a bit, killed it (had to use task manager to kill the process, in fact), looked at the debig log, and founds *lots* (1000's) of the following error messages:
[2009-05-15] [09:34:58.714] 02384 1 VolumeBitmapCache::ReloadFromCluster#101 FSCTL_GET_VOLUME_BITMAP for handle 0x00000588, lcn: 85458944 failed with error code 87
Suggestions?