Dell XPS 720 Power

Hi, I've had this Dell XPS 720 for about 11 months and within the last few months I've noticed that the 8800gt was running at 72 degrees idle and 90 degrees under load. I can only assume that it was always this way since I've decided to check the temperature relatively recently and from what I've read, that is far too hot for the video card and can decrease the life span. So I went ahead and followed a guide on how to use rivatuner. After setting AutoFanSpeedControl to 3 and adjusting some Tmin, Tmax, etc, controls I have it so that the fan runs at 40% at least gradually escalating to 100% although its never gone higher than 70% after playing a game because it doesn't get that hot anymore.

However, the very next day after setting these fan controls, my Dell wouldn't power up consistently, sometimes giving me a blinking amber light. A few days after that it just wouldn't turn on at all, giving me a blinking amber power light every time I attempted to boot up the machine. After talking to Dell support, they told me to unplug all the components (hard drive, optical drive, sound card, video card, modem, memory), and the power still wouldn't turn on. Dell sent in a tech and replaced my power supply and the machine started working again. It worked for a week until yesterday where again my machine didn't turn on with a blinking amber power light. My machine still turns on more frequently than not but I can only predict that very soon my machine will stop turning on completely again.

What I wanted to ask was whether it is possible that the higher fan speeds on my graphics card are really fooling around with the power supply as it seems to be, or is it a mere coincidence? What should I do about this?