I was pretty excited to get the preview event email. Haven't had much success since updating the client however.
The client said it did not recognize my account from previous events. So I re-registered. Then I tried to use the new, confirmed account to log in. Again, no recognition. So, I made my way here, only to find the forums and wiki do recognize me.
0.o
Did you uninstall/reinstall the game (if you're using the downloadable client)? We switched to different servers, so the client from previous events will not work. You can download/launch the game at http://www.spiralknights.com/register/thanks.wm.