start up problems
I have similar start up problems with my white 24" imac (EMC 2111). My observation is following: the lowest of the 4 green diagnostic leds is burning, then more leds are lit for a moment but without success. Also the fan (close to bottom left speaker box) rotates for a moment. This is automatically repeated a few times, until the machine gives up. Now, all leds are off.
I can repeat this cycle of trial and error by disconnecting the power cable for 5 sec or so, and then reconnect.
In the last few days, most of the time I had no success, but a few times I could get the machine back from death by just trying, although I have no idea if I will succeed next time. The machine never broke while I was working - it usually happened in the morning when getting the Mac awake. When I am sure that it is indeed the power supply, I will replace it.
Is this a good question?