5th video card slow hashrate

[BlazinBeaches]

Does anyone know why the 5th video card is only getting 575 kh/s while the others are getting 730s?  The OC settings are the same across the board.

Cards are 5x 7970s
Mobo is MSI Z77A-G45
Cards are using 16x-1x riser cables.
OS is Win8 x64 (for now).
13.6 beta drivers installed with SDK 2.8.
cgminer settings are correct.

What do you guys think

[ma_rine_sa]

uninstall afterburner, uninstall ati drivers, uninstall opencl, use ati cleaner

install another set of ati drivers, install opencl, install after burner

had the grey out happen to me few hours ago as i was trying to glitch afterburner to let me set my video cards to 300 memclock.

[BlazinBeaches]

Ok cool thanks man.  I ended up installing Windows 8 because my Win7 install was botched so I just threw 8 on instead for now.  The system recognizes all 5 cards without a hitch.