Need help, possible mobo problem!

I recently bricked my m18x r2 motherboard by usb blind bios flash, so I bought a replacement, but the problem is that, when I install the new mobo, my screen starts to show weird signs, like flashing white dots in screen background, and not long after that, there is 1 vertical line appeared on my right hand side screen, and it won't go even I power off the machine or reboot even after I removed both discreet cards and switched in Igfx mode.

The strange thing is, when I test the hdmi in port with my PC hooked up, the flashing white dots in screen background disappeared, but the vertical line remained; on the other hand, when I test the hdmi out port, everything works fine in output screen which is my PC monitor.

So I would like to know:

1, can a defect in mobo, e.g. bad monitor cable connection slot causes this kind of problem?
2, is my CPU which is 3920xm the cause of the problem? e.g. needs to resit, or bad onboard graphics module?
3, is my screen faulty? (but before this mobo replacement, it was fine, and I have even tried another screen, and it has the same problem as this 1, but without the vertical line)

I'm really confused, I ordered another new mobo and am waiting for it to come.

but in the meanwhile, it would be great if someone can shed some light on this, I hope the problematic mobo didn't do any damage to my screen, i.e. the vertical line, otherwise I might have to replace the screen as well?

Many thanks!