>>>>Nope. Actually this one is much simpler than yours was if you think about it...
>>>I think I got it.
>>>Turn one switch on and leave it on, long enough for the light bulb to heat up.
>>>Turn off that light, and turn on another just before you enter the room.
>>
>>Yep :) I knew this one from the times, I was a kid...
>
>Have you heard this one?
>
>You have 12 billiard balls.
>
>One of them is either lighter or heavier than the others.
>
>You can weigh the billiard balls 3 times on a balance scale.
>
>You need to find out which ball it is and whether it is heaver or lighter.
>
>Is this possible?

I could not make it in my mind. Tried few combinations unsuccessfully. I think, 3 times are not enough...

BTW, have you heard, that the Great Ferma theorem is solved? I don't have link handy at the moment...