About the only thing I can think of is try rebooting and going into safe mode.  Once there see if you can logon, if so then change the logon back to what it was.  Good luck.

You could try the ODNT Zapper file to see if that will remove the Logon Studio. Not sure if this will work or not.

If not then email support@stardock.com and start a trouble ticket.

This is the weekend so unless a support tech happens to check the forums during the weekend you may not get a reply (other than the auto-generated ticket number) until Monday.

Post the ticket number here in a comment.

Start in safe mode, run an Adminstrator command prompt and type in sfc /scannow

 That will restore the default logon as when I have run it, I've had to re-apply my  customized Logon when finished.

Whenever I've had trouble logging on I've used emergency software Offline Windows Password & registry editor tool, You could give it a shot. It's completely free. Just use Imgburn to copy it to a disc or place on your USB drive (if your PC supports USB boot devices). Boot your PC either using the self-bootable CD you just made or USB drive and use this tool to reset your password which wouldn't require a login. From then you can just simply set a password again and re-apply your custom logon.

You can get it from this link.

http://www.pogostick.net/~pnh/ntpasswd/bootdisk.html