I'm thinking a problem with the power supply (PSU). If the PSU isn't delivering enough power, it should send what it has to the important components, like CPU. GPU is left out, therefore you see the blue screen. Either that or...
A weak connection of the graphics card to logic board, monitor to graphics card. Disconnect the cables and reconnect firmly. I had something similar happen to my external 24" display. And reseat the graphics card (pull it out, wipe it with a cloth, put back).
see, i got the logic board replaced today while sitting at my house, and we pushed that little shnikey in all the way (video card).
so it is not connected badly, so it might be the psu as a few have suggested?
i will have to call apple and see what they can do?
iw ill keep everyone posted as apple and i chat it up tomorrow and throughout the week to remedy this!!
and no i will not lose my temper and i will remain calm, and i will repeat this over and over again and again