fans don't use a lot of power. If that's the case, then you're only JUST over the limit for your PS. try unplugging your CD drives and leaving whatever fans. If it still crashes, its a problem with the fans or power to them, not the PS.
How many watts is your PS anyway?
EDIT: another thing that just hit me is that fans operate at 12V, not 5V.
12V in a computer (yellow wires) are for anything that moves, and 5V (red wires) are for electronics.