GPU/CPU fan do not start - HELP!

Hi all

basically - did a dissassemble and clean... put it back together - GPU fan wouldnt work.
Assumed id broken it (hoover is a dangerous thing... even though i used a toothpick in there) but then after checking its power supply and assembling laptop again - CPU fan also refused to start.... i get about 15mins of use then overheat and shutdown.

STRANGE THING - yesterday i let the lappie go to sleep - on resume - the fans worked again... both of them.... perfectly... without whirring or anything like that - what the hell is going on?

i am not an expert on dissassembling.... i took most precautions - only thing i can say that ive done is go without some of the screws... i always put less back in so its faster taking it apart next time - could that be it?

I have a P-6831FX - stock - with windows 7 32bit clean install from vista about 3 weeks ago.

the fan power supply cables and plug on the motherboard look fine - no problems there as far as i can see. only real problems with the laptop are that the keyboard was having probs (getting replaced) and the power button connector cable burned out about a year ago

P.S - PLEASE PLEASE HELP ME - any ideas are welcome, ive taken the thing apart maybe 10-15 times... trying to find a problem.... and this is my only PC, and money for a new one....... is well... thats just a dream atm

THANKS FOR READING!