3 crashes yesterday, what next?

[shanner]

Hello,

I've had no problems with my 9 month old imac till yesterday when it crashed 3 times, the last time resulting in it being dead for a few hours. The first 2 times I was using Firefox and then iPhoto but I was able to start up again using the power button. The third time I was browsing again and blammo. This time the screen went black and I was unable to start up again. I turned it off and on again several times with the power button, but there was no chime despite the power light coming on.
This morning the computer came on no problem and I ran a hardware test from the installation disk and it came up 'no problem found'.
The only thing I was doing differently was that I had Skype open where it usually just sits in my Apps folder and there was a security update download yesterday afternoon.
Does anyone know what I should test for or look out for next? Any ideas?

Thanks a lot!

 

[CanadaRAM]

OK, this is a no-brainer. 9 months old -

1) Back up your data ASAP
2) get it to the nearest Apple authorized repair centre to be checked under warranty.

Sudden unprovoked black screen is much more likely to be hardware failure than it is software.

If the screen went completely dark (as opposed to the black panic screen with the "you must restart" message") my guess is a failing power supply.

In this case there is nada that you can test or do yourself that will make a difference.