Monitor issues

I am at a loss. I purchased a new computer with monitor, the monitor would not stay on. Some times it would stay on for a long time. Then it would not have a picture. If I turned it on and off many times it would eventually stay on. I sent both back to Acer for repair. Acer sent the monitor back, saying it was not needed. The CPU came back, the monitor does the same thing. I have two newer LCD mointers and it does it on both of them. I just purchased a new CPU a Gateway. Believe it or not both monitors do the same thing. I even replaced the monitor cable and it still happens. Both computers have Vista premium. Is there a Vista problem?