I've been having the same problem lately. When I click the Windows Live Messenger Icon, it shows the open chat-windows. But sometimes on of those titels gets left behind on top off all the other application windows. It's half transparent, but very annoying.

As you can see in the next screenshot the title stays on top of all the program. I can only get it away by rebooting my Pc (not in standby, or by exiting the OD program.)

I'm using Obect Dock 1.90 Plus buid 535