9800GT Fan stuck or broken?

Hey!

I've been having an issue with my gfx lately. Whenever I start playing graphic intense games, the fan will start to loose speed after a while, and sometime after that my PC will crash. Normally it takes quite long before it happens, but once it happens it will keep happening(even if I just get into Vista) until I switch the PC off for awhile.

If i press hard on the center of the fan and let go, the fan will go back to normal speed for awhile longer. But that only works if its done right after the fan starts losing speed.
As soon as PC crashes out, then not even that helps, and I can't keep an eye on my gfx all the time.

Is something expanding because of the heat, causing the fan to get stuck in its casing?
Or is there possibly something wrong with the motor? Which I really hope not. Because it works fine normally, it only starts to cut back at high temps(and it gets like untouchably hot).
Will using an app like RivaTuner help? (I'm currently at work and need to download it here to take it home)
I've had the card for months now and it never had this problem before.

Any feedback will be great, thanks!

My Specs:

Asus P5Q-D Motherboard
Intel Q6600 Quad Core @ 2.4GHz
Corsair DDR800 RAM - 4GB
Asus Nvidia 9800GT gfx - 512mb
Seagate ATA HDD - 200GB