AHH!!! THIS IS SO ANNOYING!!

[flowone_uk]

Hi guys and a happy new year to you!

i have a problem thats starting to drive me INSAINE!!
heres my system spec

Be Quiet Dark Power Pro 650W psu
Q9550 cpu
2x 2gb ddr3 corsair dominator ram @ 1600mhz
1TB Samsung Spinpoint F1 HDD
water cooling cpu and fsb
*note. i have not yet overclocked this rig in any way i have the water loop as i origionally intended to oc but need to sort out this PROBLEM*

RIGHT! heres the prob,

when i switch my pc on it wont always power up properly
the waterloop pump starts. all fans start and i can here the cpu do some initial 'clicks' but the dam thing just wont post sometimes not always. i have replaced the motherboard and as the new mobo didnt support ddr2 ram i had to buy new ram. so the mobo and ram has been replaced.
when the machine doesnt post i SOMETIMES find that turning the psu off leaving it for an hour then switching it back on does the trick but NOT ALWAYS! this is an intermitant problem and i have rebuilt the machine from scratch on several occassions. all parts are still under warranty but ill be charged if i send in a part that isnt faulty and ive already sold my old rig so i have nothing to check parts on

any ideas would be appreciated

Many Thanks in advance

and

please, please PLEASE HELP!

 

[flowone_uk]

BTW my thought is i have an intermitant fault on my psu BUT the pc always starts (fans start whirling cpu clicks away it just wont post! the mobo has been replaced so it CANT be a fault on the mobo unless im REALLY unlucky surely!

 

[rodo]

You could borrow a PSU off a friend if possible to test it, or get a multimeter to check it.

 

[flowone_uk]

It does seem like the psu doesnt it?

the thing that really confuses me is that when i swaped the mobo everything worked PERFECTLY for a month or so then it all started to go pear shaped again. is there anything else it could be?