Running 7x32

With 4 GPUs running (3x5850, 1x5830)....I can get 3 of them to work in GUI miner.  Whenever I've tried to activate a 4th, it just sits either at connecting or shows a constant mhash rate, without accepting shares.  Regardless of which GPU I activate last, this happens.  Have tried with both poclbm and phoenix. 790FX GD 70 mobo. all cards are in x16 slots