> Hooray! That did the trick. Can you explain why? The JPG
> files had a *.jpg extension -- why would HTTrack 
incorrectly
> guess their MIME types? Or was it some kind of server 
error?> 

Nope - httrack generates local filenames before actually 
downloading files (or getting redirect and figuring out 
that is was another file type), and to speed up type 
testing, some assumptions are made (like asp,php,.. => 
text/html)