Problems with HD7970 *** Importante ***

Hi there Bitcoin addicteds, i need some help from u guys, i´m having problems with my hd7970 and i´ve lost many many hours trying to solve them so maybe u guys could help me sorting it out

I have 5 rigs for mining and i was using hd6990, hd5970 and hd6950 graphic cards on them to do my work, but then the hd7970 came out and i decided to sell my old cards and upgrade to new ones

I´m using 2 kinds of mobo

Intel Mobo with motherboard Asus P67 and intel I5 with PSU 1300W Tagan

AMD Mobo with motherboard MSI GD-80 with Athlon and PSU 1000W Chieftec

I bought 7 units of this graphic cards:

http://www.amazon.com/DirectCU-1000MHz-Overclocked-Graphics-HD7970-DC2T-3GD5/dp/B00739TCH8/ref=sr_1_1?s=electronics&ie=UTF8&qid=1334290094&sr=1-1

And 2 units of this graphic cards:

http://www.amazon.com/Sapphire-Radeon-PCI-Express-Graphics-21197-00-40G/dp/B006P88VO8/ref=sr_1_2?s=electronics&ie=UTF8&qid=1334290194&sr=1-2

I was using this kind of extenders with my old cards:

http://www.amazon.com/PCI-E-Riser-Cable-High-Quality/dp/B0054CQM74/ref=sr_1_3?s=electronics&ie=UTF8&qid=1334072149&sr=1-3

So problem is that i can´t make the hd7970 work with the extender cables, in order to boot the computer i have to make about 10 times reset, and if i´m lucky getting into windows it will behave strange and will freeze, also when i start the bitcoin program screen will go black althouth the computer remains working, and no response from it.... the extenders where working very nice with the hd6xxx series cards and never had a problem, sometimes it stoped or crashes but not very often maybe 1 or 2 times a week, but with this ones i can´t even make it work, i tryed all the drivers around, all the versions, and problem remains ... so for now i gave up of extenders/Risers until i find a solution for my problem

I connected the graphic cards directly on my computers 2 in each one and still facing some problems, after some hours of work computer reboots i saw in other topic that the problem may be on CCC so i uninstalled it and i´m now testing if the computers remain stable, i use MSIAFTERBURNER to check temperatures and make overclock right now i have the ASUS on 1125/700 voltage 1112 , anyone facing the same problem Huh

Anyone know how to solve it ??

Really this graphic cards are getting on my nerves, so much money invested on them and i can´t make the systems stable, very important for me is to use the riser cables because the Asus graphic cards are very big and i can only insert 2 of them directly on motherboard

Any help would be appreciated .. i really need it ...

props to all from Portugal