Unhandled listen loop exception - InstantRails 2.0

Greetings,

I’ve downloaded InstantRails 2.0.

Run it (with default server and dbase)

Created new project,
run “Start with Mongrel”
and tried to access it through http://localhost:port/

Unfortunatelly It returns:

Unhandled listen loop exception #(Errno::ENOTSOCK An operation was
attepmted
on something that is not a socket.).

Any suggestions ??

Thank You