Wake up problem in SL with external display?

Hello all,

Just did an upgrade from Leopard to Snow Leopard on my 09 MBP. I always use this computer in conjunction with my NEC display. On Leopard, I would keep the MBP lid closed and use the mouse or keyboard to wake it up, using only the NEC monitor. Now in SL, whenever I try to wake it up the screen flashes for a second and the computer goes back to sleep. Is there a setting or something I'm missing, or simply a bug?

Really frustrating, as it's rendering it nearly impossible to use an external display. Everything else in SL so far has been great (knock on wood)

Thanks!

 

Thanks for the reply...power cord was plugged in the whole time. I did a resett on the SMC settings, and now it seems to be functioning properly. I'll be keeping an eye on it though.