refuse to boot?!.....omg...but when it boots, everything is normal like usual....this is wack, manthe motherboard is probably dying. i bet some capacitors started to bulge.
that or same thing, but for the PSU.
without spare parts you can't know for sure, but very soon your computer will refuse to boot at all.
It happened a lot before to me, at that time i used special fans with a know i turned to reduce speed. turns out those things kills motherboards over time.
was in 2007-2010. 3 motherboards in 3 years. I really hate those enermax fans !