May as well add my experience...
My setup is :
Graphics : NVIDIA GeForce 8800 GTS
Monitor : Samsung Syncmaster 226BW
KVM : StarTech 2-port DVI switch SV211KDVIGB
When I switch from my Win 7 machine to my XP machine, there's no problem. XP handles it fine.
When I switch back to my Win 7 machine from my XP machine the monitor goes black and doesn't come back until I disconnect it from the KVM and reconnect it (or reboot the PC).
Is this really the best MS can come up with - buy a new KVM?
Price of OS : £50
Price of KVM : £100
I'd rather toss the OS and go back to XP if that's the best solution on offer.
This is clearly a widespread problem.