Black screen only when turning on PC with arcade and LCD monitor simultaneously

[LEM]

I installed CRT Emudriver on my Windows PC. It runs well. Arcade monitor connected to VGA port and LCD to DVI port.
Image shows up correctly on both monitors when I turn on the PC.

Now I decided to go a step forward and installed ATOM 15. In this case, when I turn on my computer, if I have both connected, I get a black screen on both.
However, if instead, I leave the LCD monitor unplugged, the image will show up ok on the arcade monitor. After that, if I plug in the DVI cable,
image also shows up on my LCD. The opposite doesn't work.

Any ideas why this happens? I understand that during the booting process the video signal is set to 15KHz, so the LCD should be blank,
but once Calamity drivers take over, image should be displayed on both. What am I missing? 

I'm using a Radeon 5450 and also a JPAC.

Thanks!

[Max_FS]

This sounds familiar to me:
http://forum.arcadecontrols.com/index.php/topic,161571.0.html

Just take a look at my older post, maybe it is the same problem you have. I was not able to solve it with a software solution so i had to build a little hardware device that delayed the power supply of one of the screens...

[LEM]

Thanks a lot for your reply. Sorry, I searched a lot and I didn't see your post...
(btw there's a typo in the link, right one is http://forum.arcadecontrols.com/index.php?topic=161571.0 )

So I guess there's nothing I can do... except adding that delay. However, let me ask you something.
Is it the same for you the opposite? I mean, starting your PC only with the LCD plugged in? Because in that case in doesn't work for me either.

CRT on, LCD on -> Black screen
CRT on, LCD off -> OK
CRT off, LCD on -> Black screen

Thanks.

[Max_FS]

No problem 

With regard to your additional question:
I really cannot remember it precisely. I only remember that I did a lot of testing and even created an excel file to write it all down. Unfortunately, I can't find that file. I think I deleted it...
But in the end I decided to delay the power supply of the LCD and not of the CRT. So that may be a clue that it worked for me with CRT on and LCD off.

[LEM]

Not a problem, I have done so much testing that sometimes I even forget what I tried an hour before.
I think I will just use your workaround.

Regards