The issue I see is that "not much at all" was told about the computer you put these cards into.
I run into such issues weekly (or rather "Tech" does) with 300 or less Watt power supplies on many GHz computers stuffed with everything. The all common words are "it can't be the power supply" and "it worked before".
Here's my feedback. Get in your car and go 100+MPH and my bet is that something will break that didn't before. This is about what happens when we add more to our PC and don't keep up with what may seem to many a huge power supply.
Here's a simple heat test. Most machines were built, tested with just so much in the case. You might put in a drive, that 50 Watt plus video card and it will get much warmer in the case. Try it with the cover off.
I am having major problems with my system.
Before 1 month ago I was using an old nVidia GF4 64mb card on ?Gigabyte FA-7VT600-L? mainboard. Then I have bought a new video card: ?ATI Radeon 9600XT 126MB by Powercolor?. It seemed to work fine for couple of weeks. However after some time I started to have some problems, without making any changes to my system. If I played games or carried out other graphics-demanding tasks, my system would hang/suspend after 5-10 minutes and I had to restart my system. I have tested my card at my friend?s and it seemed to work fine, so I thought it?s a compatibility issue.
So 1 week ago I have sold by ATI Radeon card and bought a new card: ?nVidia Geforce FX5900XT 128MB by Spark?. It worked for 1-2 days, but after that my system couldn?t even startup. After the bios loads, the whole screen gets messed up and there are lots of lines and pixels all around the place and system hangs and suspends. So I went to the dialer and they tested the card and it seemed to work fine on their system, and they told me to buy a new power supply. I went and bought very expensive power supply, an Enermax 350W one. However the same problem was still there. So yesterday I went and bought a new mainboard: ?ASUS A7V8X-X?. And still, the same problem is there. I startup my PC, it shows the g-card information then it goes to the ASUS graphical bios startup and the lines appear and the system suspends and monitor turns black. However the system works perfectly fine with one of my old cards: ?nVidia GeForce4 MX 64MB by inno3D?.
Please help me solving this, since I am completely frustrated for spending so much many and not being able to run any graphic-demanding applications using my high-end g-card.
Thank you in advance,