NEVER run the cpu WITHOUT HSF. You never tell us how long you have that fan running on the other mobo. My guess is that the fan is faulty that there is a short within it coils causing it to drain lot more ampere thus killing the circuitry on the mobo that supplying it. If another known good fan cannot function when connected to the two 3-pin fan connectors, then I'm afraid 3-pin fan connectors are a goner. Replace the fan and connect it to one of the power leads for hd/floppy, unless you have one more 3-pin fan connector left on the mobo. You need a 2-wire connection only as for the other lead is for rpm reading but you can still connect this lead to the 3-pin connector. Make sure you know which pin.
It don't come easy.......not always.