On two Macbooks with Thunderbolt ports, 30" Cinema Displays and running Lion, keep asking if I really want to shut down.

Strange how on the same day, I have two users reporting the same problem. Really annoying as the dialogue keeps coming back up asking if I want to Shutdown, restart, cancel or sleep.

Tried resetting the pram on both but, that didn't help. When I disconnect the Cinema display from both macs, the dialogue box stops coming up. For both macs we are using Apple's dual-link dvi to mini-displayport adapter.

This was not a problem under Snow Leopard. Is there a known incompatibility with the older Cinema Display, Lion and Thunderbolt? Is my only recourse to purchase Thunderbolt displays? Has anyone else encountered this issue?