Okay, I am a new victim. I swapped out the power supply and it worked.
However, I think my solution and others listed are work arounds. I believe this is an "Apple" issue that Apple engineers need to fix.
I have the following equipment:
7 year old 23" CD purchased second hand (presumably a month after original owner purchased)
a year old iMac running 10.6.8 (purchased new);
a 7 year old Pwr Book (purchased new)
I purchased the iMac so I could run Windows (a POS) in a VM. In other words, my Pwr Book still works.
I first experienced the CD issue 3 weeks ago after a power failure. I tried the monitor with Pwr Book and it did not work. Therefore, I thought the failure may have fried my "brick" power supply so I purchased a used one (I tried using an ohm meter, but leads were too thick).
In the meantime, I used a new Dell display without issue.
When I received my new/used supply, I was able to use the monitor. However, I went to lunch and come back to find that my monitor will not come out of sleep mode.
I find this posting. The only suggestion I tried was waiting 15 mins, which did not work. Therefore, I tried my initial/original pwr supply and low and behold, my supply comes on.
Based on the responses, I changed my display settings to no longer go into "sleep" mode.
Time will tell, but as I stated initially, I truly believe this is an Apple issue associated with either new hardware (ie intel), new OS, both or something totally different.