The password for the members forums is not working for me. Everytime I click 'Check Authorisation' it goes back to the same page.

In your internet explorer,

Go to Tools - Internet options - go to 'Privacy' - click 'Advanced' - click third party cookies prompt and it should work :D

You also have to allow cookies from s4.invisionfree.com (this site), but any other cookies it wants to put on your computer are probably nasty and I would recommend not allowing them.