This problem is widely reported on Apple's Support discussion groups, I haven't checked it lately but last time I did there was no known solution.

Sometimes I can get an external display to work even if the main display won't, but it's not perfect. I have to reboot the machine to get the main display back.

I really hope Apple fixes this soon, I've never had so many issues with sleep with a Mac as I had with this MBP (2.4GHz), my first Intel-based Mac. Actually I've pretty much never had any issues with any of my Macs before this one.