Funny taht you'd mention that... About a week ago, when the northbridge fan on my Abit board started making more and more noise (at the time I din't know what it was), I opened the case, tired to find out what that was, then turned off the pc, then turned it back on. And then... the northbirdge fan was stopped!
I took it out to take a closer look. I think they used a very low quality fan. Also, I could tell that they used lubricant of some kid to keep things smooth. But I'm guessing that the lubricant atracted dust and the whole thing just clogged up...
I used Radio Shack pots cleaner & lubricant spary and the fan now runs again.
But I'm gonna get a diferent one, probably blue orb (because it looks so cool, lol) to replace the stock fan. I have a funny feeling the stock fan is not gonna last long.
The moral of the story is, I guess, keep an eye on that northbridge fan!