Benq xl2420t "No Signal Detected"

[gcnx1234]

First off I use my BenQ with a DVI cable. One night I put my comp in sleep mode. When I got back on and turned my BenQ on it said "No Signal Detected." I tried re-plugging in the monitor and making sure on both ends of the cable were securely attached. Still didn't work. It works though if I connect it with a VGA cable, but then when I use it in CS GO I get black screen moments. I turned the computer off and retried the DVI cable, it worked but then shortly later I got the same error. I then tried a hdmi cable and it work for a bit until I put the comp in sleep mode. I tried shutting off the computer and re plugging in the DVI and hdmi cable and selecting whet connection I'm using on the monitor, but still i get the "No Signal Detected" error.
Please help me find a solution, thank you.

Update:
I tried taking out the RAM and putting it back in, still no success. I unplugged the DVI cable and connected the DVI cable to my old Samsung monitor and the monitor works, so that means the cables functioning correctly. Does this mean its the BenQ monitor that is the cause? I noticed before I got the error that the BenQ monitor would frequently get dimmer as I used it as if it was on some auto dimmer.


Here is my computer setup:
Windows 7 Home Premium 64bit
Motherboard - ROCK | FM2A78M-HD+ R2.0 RTL
Processor: AMD A8-7600 (APU)
RAM: G.SKILL Sniper Series 8GB (2 x 4GB) 240-Pin DDR3
Monitor: Benq xl2420t

 

[Phillip Corcoran]

Your post strongly suggests to me that the Benq monitor is faulty - - what clinched it for me was when you tried a different monitor which worked fine - - that's fairly convincing proof I would say, that and the fact that the Benq display kept dimming.

It's not a brand I would choose anyway.

 

[gcnx1234]

Ok, now I have no clue.... I'm using up to date AMD drivers and when I use HDMI for the BenQ and select detect displays after turning my BenQ on, it will show up and I'm able to use the monitor. But if i turn off the monitor or shut down or go into sleep mode, I have to redo the 2-3 minute process of using a separate monitor to do the AMD Catalyst detect display for the BenQ