I tried to mirror <http://www.merck.com/pubs/mmanual/> 
and it has images located on another server, which are 
coded as:

<http://a248.e.akamai.net/7/248/430/20010501022008/www.m>
erck.com/pubs/mmanual/tables/t135_2.gif

for one example. HTTrack tries to download this 
picture from:

<http://www.merck.com/a248.e.akamai.net/7/248/430/200105>
01022008/www.merck.com/pubs/mmanual/tables/t135_2.gif

and gets, obviously a NotFound error.

Looking forward to a fix:)

Philip