I can confirm this. The error messages look similar here.

Ubuntu 13.04 64bit using Google Chrome.

Workaround: use Firefox and set it as standard browser first.

When you don't want to do that, proceed like this:

1) start firefox
2) start webhttrack, but close the browser window in the other brwoser
immedeateley
3) webhttrack should now still be running
4) go to this url in firefox and set a bookmark: 

<http://127.0.0.1:8080/server/index.html>

5) proceed like normal.

Next time at step 4) you can use the bookmark

Works on my machine ;D