> still when downloads are interrupted by line 
> disconnections - i choose continue interrupted download 
and 
> it checks all the files and updates the existing ones 
too, 
> it slows things down tremendously and i cannot get it to 

First it is perfectly normal that httrack scans the local 
file structure ; but this should be quite fast (except if 
you downloaded thousands of pages)

Ensure that you cleanly interrupted the mirror after the 
line was shutdown: select cancel and WAIT for pending 
connection to close (or break them using SKIP buttons) ; 
this will allow downloaded files in background  to be taken 
in account.