Is the problam his power supply? Or could it be this:
the green circle is where this is connected to the power supply, the black connector goes to the video card. Im no electrical engineer, is it ok to have something like that connected within it self? That awkward wording I know. If I was installing this I wouldve run everything in a linear way, not in a circle like this.
Connect those two 5v power connectors to two different (separate) connectors. Your problem might go away. it sounds like it isn't getting enough juice or it is running a little hot. Either one would do it.