Sometimes when my machine resumes from sleep mode Aero doesn’t work and I lose transparency etc. It seems to be related to nForce chipsets… Remind me never to get another one of those, they are buggy as hell. If you check the application event logs there is an error 0x8898009b from DWM.
The fix is the following two commands to re-start the service:
Net Stop uxsms Net Start uxsms