> Just checked -- HTTrack destroyed 3 directories 
total 
> (about 50 megs, or otherwise the better half of my 
> day's downloading).
> 
> I think it's becaues the server is giving 'Error 
302: 

Darn, this shouldn't be! (the 302 status is managed by 
HTTrack)
Any hints on the hts-log.txt file? Any errors? A 
common problem (I didn't solve yet) is when a site is 
temporarily unreachable (for example, quota is over, 
or directory is forbidden) - in this case HTTrack 
synchronize the directory as it is, and therefore 
deleted all files downloaded before.. 

Use 'do not purge old files' to avoid such behaviour, 
but this won't fix the re-download problem