Heh, about that... it's a Corsair TX750M. I have to undervolt the cards to 1.1v or the PSU shuts down.
Ohhh, interesting!
The Corsair TX750M is a good unit. It's manufactured by CWT (a decent PSU OEM), I believe . I'm running a TX850v1 and a TX850M myself at the moment. That said, it may still be that you're overtaxing the poor thing.
You're probably right at the point before the OCP kicks in but after the +12V rail falls wildly out of spec. This can certainly cause the issue that you're experiencing (but don't take this as a 100% positive diagnosis). Again, if possible try monitoring your +12V when you start cgminer and see if it's going wild. Also, if it's not too much trouble, change nothing except remove 1 card from the system and try firing up cgminer. If it runs perfectly then I'm going to say it's time to upgrade that PSU.