It appears that launching httrack in a batch file loses the security context.
Here's my batch:

set httrack="C:\Program Files (x86)\WinHTTrack\httrack.exe"
set output="C:\myfolder\mysubfolder"
set options=http://user:password@site.com +*.png +*.gif +*.jpg +*.jpeg +*.css
+*.js -ad.doubleclick.net/* -mime:application/foobar -*robots* -*public*
-*private/something* -*private/somethingelse*
%httrack% %options% -O1 %output%

Running this in the command line works just fine. 
Running the batch results in "401 error('Authorization%20Required')".

Is there a way out of this? Thanks you in advance.