I have the windows firewall turned on, and use Free AVG anti virus. As I use a router I have been told this should be ample security.
I have just tried the Opera Browser and the site loads in that, but not in Firefox, IE8, Safari or Google Chrome!!!
When i look at the built in error console in Opera, there are loads of errors. One of which relates to Java. Might try to reinstall Java, see if that has any effect.