For the short term I'll exchange either the network card or PSU between my two IIsi's, once I have both of them. However, when I saw this flash, it was almost wholly outside of the case, as if the flare of whatever vaporized was channeled out by the exaust fan - the IIsi doesn't have any vent on it's rear that opens to the PSU.

What precautions should I take when inspecting the PSU? I don't need a capcitor to discharge into my arm.