I have discovered the cause of the magic smoke release. It explains quite a bit (including why the flash occurred outside the case) and it may surprise you.
No, it wasn't the PSU, it's perfectly fine:
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It was the NuBus riser card:
Apparently, when this cap (or whatever it is) blew, it sent a massive amount of voltage up the network card ribbon cable (on left). Then this excess voltage found the path of least resistance, which I believe is the RJ-45 outlet. This would explain why I saw a flash outside of the case, not exactly at the psu.
I didn't see this until I was about to pack it up - I noticed a very small scorch mark right on the pcb itself, with an orange shard of capacitor nearby. The motherboard itself has no orange-colored capacitors, and the PSU has none that are that small. A little more searching and I discovered the rest of the carcass on the NuBus card.
No, it wasn't the PSU, it's perfectly fine:
Uploaded with ImageShack.us
It was the NuBus riser card:
Apparently, when this cap (or whatever it is) blew, it sent a massive amount of voltage up the network card ribbon cable (on left). Then this excess voltage found the path of least resistance, which I believe is the RJ-45 outlet. This would explain why I saw a flash outside of the case, not exactly at the psu.
I didn't see this until I was about to pack it up - I noticed a very small scorch mark right on the pcb itself, with an orange shard of capacitor nearby. The motherboard itself has no orange-colored capacitors, and the PSU has none that are that small. A little more searching and I discovered the rest of the carcass on the NuBus card.