Hi Jason,
I have confirmed trying all the above mentioned steps and did not get it resolved.
1. AC cable is connected.
2. I am using an Apple DVI to DisplayPort adaptor
3. Done
4. Done
5. Only one display port is used, an the Display Port works
6. I tried using another monitor and projector, both have the same issue
7. I reset the PRAM and it seem to help for about an hour and went back to the same issue
8. Resetting the resolution does not help
9. I upgraded to Yosemite to see if the issue is fixed but was unsuccessful. I Time Machine back to 10.9.5
I am considering
-Trying another adaptor in case mine is a defect
-After researching online, it seems like the issue is software related. So reloading Mavericks 10.9.4 to see if it would fix the issue.
Any other suggestions? Thank you so much for your help.
Thang