Today I was unable to get ddo started on my Windows 7 system. The initial ddo launcher would run fine, able to enter username/password and select world. After that the fat portion of the ddo client locked up and never completed loading, stuck on a white screen--never showed any loading graphics.

Reviewing my system logs there was a single update automatically applied to my computer last night, windows security update kb2753842. It affects opentype fonts.
http://support.microsoft.com/kb/2753842

I uninstalled the kb2753842 update using the standard windows uninstall process, after which the ddo client worked fine again. I made no changes to my system attempting to resolve the problem other than uninstalling that security update.