SY-P4I875P Dragon 2 Won't Boot WITH +12V 4-pin.

I've got a SY-P4I875P Dragon 2 with a 2.8 GHz P4 that has worked
reasonably well for the last 3 years. Occasionally it would just shut
off on its own, but after turning the power supply off and on again, it
would restart. Last week it failed, and no longer boots. I unplugged
all the unnecessary peripherals to test if the power supply was just
overloaded but no luck. With the board, I get power in the power
switch, and the standby LED is on.

However, I found that if I unplugged the 4-pin +12v connector, I could
get a partial boot. I changed the power supply to a 500Watt Antec
SmartPower 2.0, but found no new results.

I'm wondering if anyone has had this experience, and if there is
something that can be done, or if the board is shot and I need to get a
new one.