Trouble after clicking on a server

Just resubbed, and I'm having trouble getting back in. I can login fine, and indeed could play fine until I swapped to windowed mode. Now every time I click on the server, the game freezes, usually on the server select screen but sometimes just after as the first character is rendered. I've updated DirectX and my card's drivers, but I am running Vista. Is there any way I can fix it or, barring that, just get it back to fullscreen without getting into the game proper?