Help. Boots to a black screen with white cursor after working fine

[lemjello]

sorry, I think I originally posted in the wrong forum.

I built this system using unibeast and multi beast. I'm on 10.10.4. System was working fine yesterday and was ready to deliver to customer. The last thing I did was run onyx. This is after a fully working system, all software installed, many reboots, then, convinced everything was fine, I ran onyx and shut down the system.
Today, I went to start it and it gets to the apple screen and the line gets about halfway, then the screen goes black with nothing but a black screen with white block cursor at the top left of the screen.
I tried booting with numerous combinations of boot flags, but, it just keeps going to black screen.
I tried starting up with usb drive, but the same thing happens.
This is so weird because everything worked perfectly yesterday and now, nothing.
I tried using disk utility to fix permissions and repair disk.
Any ideas?
Other specs are ha h97 d3h i5 4460 2 4gb sticks of ram and 1 240gb ssd. 500w PS. Tp link wi if card. Asus DVD burner.
I'm open to any suggestions as I really don't want to reinstall all the software if I don't have to.
The MB bios has been updated to the latest (F6)
Thanks in advance

 

[lemjello]

After nothing working, I decided to install fresh. It's now up and running, but, the only way I could install was with the RAM set to 1333 instead of 1600. I wonder if I had changed the speed before re-installing, if that would've fixed the problem. I will try first to run a mem test, then see if I can up the RAM speed to 1600

 

[lemjello]

BAD RAM. Corsair Vengence 2X4GB. That seems to be the issue. Tech Tool reports one stick of the 2 has something funky going on. Other than that though, everything is working, finally.