This problem is normally associated with the 5V female connectors on the ATX not making good contact with the male on the mobo. The output of the PSU will probably be fine. To check whether this is the cause; with the system running feel the side of the ATX connector at the top and see if its warm. If it is then thats the cause. Using a multimeter measure the output of the 5V (red) on one of the spare molex connectors. If you want to go even further then look for the MOSFETS around the CPU. They are square and have 3 legs. They should be in pairs and you will probably have 6 of them. Again using the multimeter with the system running under load and taking the negative off the case put the positive lead on the center pin and get a reading off each of them. Make sure you only touch the center pin! half will read +-2V and the other half will read the same as your 5V line on the monitor. If you want to boost the 5V find a female molex connector and then solder the 5V line to one of the center pins of one of the MOSFETS. Must be a 5V MOSFET that you have measured. If you get the wrong one you can look for a new mobo. If this improves it but the reading is still too low you can make another connection to another 5V MOSFET.
If you want more info on this;
http://forums.overclockers.ws/vb/sho...threadid=58333