new build doesn't start first time or restart automatically

Vista 64 business
Asus m2v
Athlon 64 3600+ x2
saphire X1550 DDR2 256mb
corsair DDR2 XMS2 2GB

*Maxtor IDE HDD
*an old v90 dialup(not actually in use)
*A USB2 PCI card
*Q-tec 650w psu

*Are all from previous build.

The problem is quite simple. When you press the power on button fans come to life and the power/activety LEDs lightup but nothing else happens, when you hold down reset everything then boots correctly.

When Vista was installing and it needed to restart automatically, Vista would turn off but then nothing else happened. Again you would have to reset manually -then Vista rebooted and continued.

Sometimes when your shutdown the same problem occurs -Vista turns off but the computer doesn't.

I have used all the latest drivers and flashed the mb. Vista hasn't crashed or had any other problems (so far). The PSU is from my previous machine and never gave me any problems, with actually more PCI card etc.

from pcprobeII:
Vcore: 1.12v
+3.3: 3.38v
+5: 4.95v
+12: 11.49v
cpu: 26c
MB: 27c
CPU: 2973rmp

I have build a couple of PCs now but am certainly no expert, any suggestions would be welcome.

thanks

I should of pointed out that I am using a 20-24 pin converter/adater on my psu.