Hello,

I recently upgraded to KDE 4.5 and noticed that the cover switch effect for window switching is now not displayed in 3D but is flat, with the enumerated windows shown side by side, flat, without the slanted windows on the right and left hand sides as they were displayed before the upgrade.

3D is working just fine. In fact, the Flip Switch works perfectly in full 3d, so I don't think I'm suffering from a OGl or driver issue (using Nvidia 255.x, tried 195.x too; latest stable Xorg server.)

This looks more like a configuration issue of some kind, one which I'm not qualified or knowledgeable enough to investigate and resolve.

Anybody out there willing to help me get this wonderful eye candy working again?

I had the same problem.
You have to disable the functionality checks in Systemsettings -> Desktop Effects -> Advanced
and also disable and reenable desktop effects one by one, applying the disabling before reenabling. Suspending compositing seems not to be sufficient.
By this way I got the cover switch working like previously.
Hope this helps!
Don Christophe