The free Webinator must have access to the Internet to run.
(This may sound like an oxymoron, but some people have
internal webs.) The Webinator checks with the machine
license.thunderstone.com on port 10003 to validate it's license.
You'll either need to place the walker outside the wall, open outbound
communication to port 10003, or purchase the commercial version ( which
doesn't do this check ).
Its probably because you're behind a firewall. The free version
of Webinator must be able to contact ls.thunderstone.com on port
10003 before it will run.
Run it from outside the firewall, open up port 10003, or buy
the commercial version.