> Most GIF/JPG files are being created with zero-length.
> (The HTML files are all OK)
> Some are OK, and if I run the project again more files
> arrive OK.
> It seems to me that HTTrack is being 'impatient' and
> every time I run it again it gets some more files.

Two problems detected:
- the site does not properly handle keep-alive
- httrack does not properly handle broken keep-alive, and 
will not issue any retry

I will fix this problem (fixed in the current beta-7 for 
Unix/Linux) soon, among with other details