[Sauvblanc]

At work, I plug my MBP (2.6 GHz, 15") into a 20" ACD and also a Maxtor external HD. Under 10.4 I could use the ACD with my MBP in clamshell mode i.e. with the lid down. After installing Leopard (only after 10.5.2 came out) I initially had no problems running the MBP in clamshell mode.

But recently I can't seem to do this anymore. When the MBP is hooked up to the ACD and turned on with the lid up, everything is fine, but as soon as I close the lid, the computer goes to sleep, as it should. But when I try to wake the computer up using my external keyboard, it will wake up briefly, the ACD will come on, and then the MBP will go straight back to sleep and the ACD goes black. This goes on ad infinitum. The MBP is hooked up to the power adapter so it's not lack of power.

The problem seems to have started-and perhaps is related to-when I was working at home, just on the MBP (no ACD or Maxtor) and shut the lid to put the computer to sleep. Without my being aware of it, the computer had in fact not gone to sleep, and I only found out when I used it a few hours later and found the battery completely drained and the computer unresponsive.

Whatever happened then completely borked the clamshell mode in a number of ways. I've managed to solve most of them but not the problem above.

I have tried zapping the PRAM, resetting the power management, fiddling with Energy Saver settings, everything I can find by looking online but none have helped.

Any suggestions on how to get proper clamshell mode back? Thanks!!

[Sargasm]

I would just leave it slightly open, as running it in clamshell mode is bad for heat dispersal.