Hi,
I just received my graphics card (HD 7750).
I proceeded to install the graphics card in the x16 top slot and the WLAN card in the x4 slot (bottom). The system shows the same behaviour as before, it won't boot.
If I switch the cards around, everything works fine.
This is obviously not working as intended, since my graphics card is now crippled to a PCI-E 2.0 x4 slot ....