I get the same error.  I can access the website form my browsers and I wrote
the web site and I know it does not have security, still I get an error. 

As a test I tried thiss atain this forum
<http://forum.httrack.com/readmsg> 

The popup message is this: 
---------------------------
WinHTTrack Website Copier
---------------------------
* * MIRROR ERROR! * *

HTTrack has detected that the current mirror is empty. If it was an update,
the previous mirror has been restored.

Reason: the first page(s) either could not be found, or a connection problem
occured.

=> Ensure that the website still exists, and/or check your proxy settings! <=