PSU Problem ?

[Morts]

So, last night my computer decided to turn itself off and then on/off/on/off.
I figured i would give it a days rest, but now when i try to turn it on, its like it cant put out any power, no power to the harddrive, fans barely running, and the CPU fan you can hear power up and down.
The PSU light on the back keeps flashing green.
What i find weird is that when its turned off, and i hold down the PSU test button, everything powers up just fine.
What exactly has gone wrong here ? :06:

[Gerald]

It sounds like a PSU problem in what you describe ... how many watts is it?

[AVGWarhawk]

The PSU or the power button itself. I ran into a shut down issue only to find the 10 cent power button on the case was bad.

[Tchocky]

PSU make and model?

Check your connectors and wires first of all :)