ok since Maintenance was last night I would suggest trying to manually install the patch from here... and then scroll the page to see the pictorial instructions on how to properly install it. If that doesn't work there are few more options.
You can go into the game folder and run a file called _Launcher.exe (they put 2 launchers in the game in case the first one goofs up on occasion..it happens)
You can try this... GS MadMadeline's Guide Launcher Patch Failures
and if after that it still doesn't work, I would suggest a full clean uninstall/reinstall by doing the following...
Make sure your system meets the minimum requirements.
Update your OS with all current patches, here:
Update your DirectX to the latest version, here:
Update your drivers to the latest version.
(Location dependent on your hardware)
Do a complete uninstall of your game. If you have problems with the uninstall, delete the directories, and use something to clean up the registry (http://www.ccleaner.com/)
Re-Start your machine.
Defrag your hard drive
Download the latest client
Re-install the game. Log in, patch, play.
Once this is done, its also recommend check out the manual patch thread
I hope this info helps you and that you get to play