Sli problems

my pc specs are:

xfx 750i sli motherboard
q9450 cpu (oc 3.1ghz)
xfx gtx 260 black eddition x2
6 gig ddr2 1066 (a pair of corsair dominator 1066mhz and a pair of ocz 800mhz with the cooler that came with the corsair dominator)
620W Coolermaster Real Power M620 Modular PSU SLi

I just recently added the second gpu and the PSU is pretty low wattage for that setup but it has been working on ever game I have apart from Crysis which shuts down after about 5 minutes of running it. I'm almost certain it isnt a cooling problem as the absaloute maximum I have ever seen my cpu core temperature go to is 60oC and thats the same for both my gpus and that was on a very hot day and the central heating was stuck on  . I would have been certain that it was my psu that was the problem but when I played crysis at the same settings (all maxed out with extreme quality mod) on windows 7 64bit, as oposed to vista 64 bit that I get the pc shutdown on, it runs with no problems other than a strange lypsyncing but that I get on all windows 7 games. I can also play any other game totaly maxed out on windows 7 or windows vista: Empire total war, Fallout3, Everquest 2, batman arkham asylum, lotro ect  . Would appreciate any ideas. Also the modular psu I had only came with 2 6 pin conectors so I'm using 2 molex to 6 pin adaptars for the second car and they are both on a fairly long daisy chain of molex connectors and I was wondering if that was a problem also