Yesterday i had a problem with the windows border decoration, when i download a theme for the windows border decoration and install it, and try to change it. At the first moment all works fine, i can work with mi xubuntu, but when i restart or close session and i try to open something that use the border decoration of kwin, the screen seems to freeze, the only thing that seems still works is te mouse pointer, but i cannot click on the other desktop stuff, this problem only occurs when i download a theme and i assign it to be my windows border decoration, with the default decorations this does not occur, i don't know what happen, but help with my problem is well welcome.

kthulhu@kthulhu-M1110M:~$ kwin --version
QDBusConnection: session D-Bus connection created before QCoreApplication. Application may misbehave.
Qt: 4.8.6
Plataforma de desarrollo de KDE: 4.13.3
KWin: 4.11.10

P.D. Sorry for bad english.

Sounds like a problem with the Aurorae engine on your system.
Which graphics card and driver combination do you use, and are desktop effects activated within KWin?

in system settings->desktop effects->advanced Qt graphic system set it to Raster instead of native solve some problems with windows border and menus.