iMac 27" Black Screen Error

[Kritzmire]

Whenever I start my computer up it is white for a second then immediately turns black.
The computer is still on, the screen is just putting it self to sleep it seems.
I forced it to sleep with cmd+opt+eject then woke it up. It went black after a few seconds so I put it to sleep again then reduced the brightness of the screen to the lowest and its staying on.
Anyone know how I can fix this?
Someone at a local Apple retailer said it's a problem with login scripts or something idk...

 

[Kritzmire]

The guy at the apple retailer store said he can fix the computer for $49.99 and its generally a same day repair. I couldn't get him to tell me the fix though :/

 

[Kritzmire]

I guess I'll take it in and see if it can be fixed for $50.