Running program on Ubuntu 6.10 (Edgy) with Firefox 2.0.01

Httrack works wonderfully, but when I use Webhttrack it fails.  This is what I
get when I try to run it from the command line:

bob@ubuntu:~$ webhttrack
/usr/bin/webhttrack(6047): launching /usr/bin/x-www-browser
/usr/bin/webhttrack(6047): spawning regular browser..

run-mozilla.sh: Cannot execute /opt/firefox/x-www-browser-bin.

/usr/bin/webhttrack(6047): waiting for browser to terminate..
 
Presumably /usr/bin/x-www-browser is used in both Httrack and Webhttrack, so
why do I have a problem, and more importantly, how do I fix it?
TIA,
Bob