Im have had the same issue.  don't know whats up with the multithreading.  It
always limits my downloads to 8 but when i put in a list of links it sometimes
limits it to 1 so i just open twenty or so instances of httrack an run each on
the same project with a different set of links i feed it to download.  this is
obviously a very cpu and memory intensive way of doing it i just wish someone
knew why it did this and there was a way to set the threading without it being
changed.  believe me i know what the server im downloading from can handle so
it sucks that sometimes we either cant multithread or were limited in the
number of threads.