I am going to ask a series of questions here to try and help you. If you do not answer them, I cannot help.
Are you getting passed the login? If not, at what point does the game go back to the desktop, and be very specific.
Do you get the arena list?
Does the game dump you back when trying to connect to an arena?
Did you remove the 'cache' folder?
Did you re-allow the game back through the firewall after the patch?
Did you try removing the 'skins' folder.
I am asking about removing the folders above just in case you have any corruption occur.
Did you try renaming the 'settings' folder?
I am also assuming you allowed theauto-updater to install the patch. Was any anti-virus programs running at the time?