Another solution found
Ok, so you'll get (on Internet Explorer 8) an error window with a "Diagnose Connection Problems" button. Click on that and after a while you'll get a report.
In small print, on the lower left part of that window, you'll see a link (in blue) that says something like "detailed information". Upon clicking that, you'll be able to read what port was blocked...
The remote computer isn’t responding to connections on port 394, possibly due to firewall or security policy settings, or because it might be temporarily unavailable. Windows couldn’t find any problems with the firewall on your computer.
write this port down and go to your router set up. Ussually, you need to open a browser window and type 192.168.something.something
find the firewall settings. you may need to go into the advanced options
Now... create a rule using the UDP/TCP option NOT the IP otion. and make sure (if there is a enable checkbox) that enabled is checked. Next, put the port you wrote down on BOTH range boxes (for example: 394 to: 394) allow inbound and outbound. and click on the "apply" or "add" button....
you should be able to access the problematic website.
Hope this helps.