Green light on The mobo is on/PSU good but PC only Powers on Sometimes

[imran_21d]

My PC Spec's:
Motherboard: Intel DH55TC
CPU: Intel Core i7 870 2.93ghz
Ram: 6Gb Ram DDR3 (2+4)
HDD: 4.250Gb (2x2tb+250gb)
GPU: ASUS 450GTS 1GB GDDR5
PSU: Gigabyte 585W

Problem: When The power goes out due to failure or outage after it's back sometimes it doesn't start, it only starts after several hours/day or by some miracle like for example in this video my Pc Stop turning on after the power had went out for the 4th time in a day (6pm) after that it only started (6pm just a coincidence) the day after witch the power had gone out 3 times!!! I don't think its a big prob cause if it was It wouldn't start anymore....Plz Help Me!!!

UPDATE: Now I have been using normally for 4 days straight cause there were no power outages, but monday around 6pm the power went out for 5min and when it came back the pc did not start and it hasn't started since, it has passed almost 3 days now and still nothing i even bought today a UPS so every time the power goes off i still have time to shut it down proporly but i dont think it will be compatible i boutght a 650va....Guys Plz Help Me!!!

Here is a Vid to better understand what i am dealing with here:
http://www.youtube.com/watch?v=bJm39bamdGU

Thank You in Advance!!!

 

[crewton]

UPS should help you a lot. Did it come with software to automatically shutdown when it feels a power trip? Otherwise, you should have enough time to manually shut it down assuming you are home when it happens.

 

[imran_21d]

no i didnt, and now its not turning on anymore its been 4 days now today i even tried the green and black wire atx trick and everything powers on but it doesnt boot