Moniter Will not start says It's sleeping

When I try to start my MAC PRO most recent edition Mountain Lion, the Moniter will not start. I get an error message that ironically say,

that the moniter is sleeping, please adjust with System Preferences. Well, with out a functioning moniter how can I even see them? I tried

lots of things, including trying to re -start, and holding shift and restarting holding Option, +P+R keys. No luck. Any Ideas? (PS, moniter does start, and the green light comes on, but screen is black, except it briefly gives me that error message.