> When I tried to mirror some pages of <http://tldp.org> I 
> found that it would download multiple copies of some 
> folders, each time appending an additional underscore.

Can you look at the file hts-cache/new.txt and search for 
the first occurence of the "underscored" directory? (like 
the linuxfocus_ one)
Then, copy this line and send it back to me 
(roche@httrack.com)
The line contains various useful information to debug the 
problem.