How to break out of a loop?

I am caught on a webpage that throws up an authorisation window for an 
ftp link that requires a username and password.  While that window is 
open I cannot do anything with Firefox - change tabs, close them or even 
close Firefox.  If I click OK or Cancel or just close the box I get 
instantaneously another Alert box saying "530 Sorry no ANONYMOUS access 
allowed".  While that box is open I still can't do anything with 
Firefox.  If I click Cancel or close the Alert box, the Authorisation 
box instantaneously replaces it and I am back where I started.  The only 
way I have found out of it is to shut down Firefox from the Task Manager 
but there must be another way out - isn't there?   What I really would 
like to do is shut down the one tab causing the problem but I can't.

It opens without problems in IE7

If you want to try it the offending web page is 
http://www.leohostel.com/index_files/leotours.htm
 
-- 
Tony

"The single biggest problem in communication is the illusion that it has 
taken place" 
George Bernard Shaw