This might not be causing the problem but what power supply are you using? I looked up the watt usage for a 6950 and its 312 at full stress which x5 is 1,560 watts and that doesn't include the mobo hd ect.
Silverstone Strider Gold 1200W. I have plenty of headroom. Also, the miners crash when I try to start them when there is 0 load.
I'm kinda confused how do you plan to run 5 6950's off a 1200 w power supply if when they are mining each card runs at 312 watts? I may have that number wrong but I looked it up here:
http://www.guru3d.com/article/radeon-6950-6970-review/11Does it crash the moment you start mining with one card or when your mining with 4 cards and you begin mining the 5th?