Computer booting with no post

Hi, i've been having this problem lately where my computer wont post randomly.
I'll turn on the computer but it wont post and all the fans will run at 100%.
I'll also see the red LED on the motherboard signalling a CPU overheat.

Heres the thing...
Sometimes the computer DOES boot and i check the CPU temperatures and they're in moderation. It seems to be completely random whenever it does boot and when it doesnt.
I've tried reseating the CPU Fan and that helped for a day or so, but not its back to normal, wanting to die.
I don't know whats going on, whenever the computer doesn't post, i try to feel the temperatures of each of the components with my hand and they don't feel like they're making any heat at all.

I can only guess that this is some kind of problem with the motherboard's temperature sensors but thats just my guess.

Heres the list:
Intel Q6600 at 2.4Ghz
2Gb of Corsair RAM
700w OCZ PSU
EVGA 8800GTX
Intel Bad Axe 2 (D975XBX2)

UPDATE:
Okay, so i was getting frustrated and tried to see if my CPU fan was being stupid again so before i booted it up i tried to shift it slightly in one direction to see if it was tilted in some way. I slightly tilted it to the left and it turned on. I then heard 4 beeps with 2 beep successions, kind of like "Beeeee booooo" then "Beeeee booooo" (yeah, i couldn't think of an analogy). The computer then said that the CPU shut down due to a thermal event on the start-up screen.

Okay, so by now i would know whats going on except for the fact that after this short episode, my computer now turns on fine until i leave it off for who knows how long. Maybe 30 minutes to 2-hours? Should i just buy a new CPU fan?

Thanks for the reply.
I have one more question,
Usually whenever a CPU overheats, it at least turns on for a few seconds then the light comes on, normally.
With my problem, it simply boots up to an overheat, like it was waiting in surprise for me.
Do you think maybe its just not contacting the CPU enough on startup and its having some weird kind of thermal problem?

Oh yeah, i have a Tuniq Tower, its not a pushpin like the stock cooler i had.

-I currently have a Tuniq Tower.
-Yes i am using Thermal Paste
-When i get an "Overheat" the fans are all spinning at 100%
-I couldn't find any reference to a red LED either, but there is one next to the CPU that turns on whenever it overheats.

The thermal paste and cooler have worked fine for 2 years and now it suddenly started this problem out of nowhere.

Thanks for your reply and help.

K try this:

Unplug your hard drive, video card, DVD drive, and ONE STICK OF RAM, leaving only your CPU, CPU Fan, and ONE stick of RAM connected to the computer.

Try turning it on a few times(I'd try 5) while waiting a few minutes in between each turn on to see if the computer will get past post 100% of the time.

Then switch that one stick of RAM to another slot and repeat.

Then switch out that stick of RAM for the RAM you took out earlier and repeat the above 2 steps.

Put back both sticks of RAM.

You can then connect your hard drive in and see if you can get past post 100% of the time while waiting 1-2 minutes in between each power-on.

If you CAN'T, then that might mean your hard drive or your PSU is failing. I'd go with the PSU since they fail, hard. -_-

If you CAN, then go ahead and plug the video card back in and connect it.

What this proves, if you can get your computer to post 100% of the time with just CPU+RAM, is that your CPU and RAM aren't what's causing this no post.

If you suspect it's your HARD DRIVE, then try using that hard drive on another computer, see if it'll boot up 100% of the time. If it does, then it's not your hard drive, most likely, again, your PSU.

Hope I've helped.

P.S. I'm experiencing the same problems except CPU overheating. it sometimes takes me 30 tries to turn on my computer and get past post.