The good new is that it is not necessarily a CPU failure click here as others with this problem have found that it is a generic answer given by some Asus boards.
The bad news is that the fault may be hard to pin down and could be related to the graphics card or the power supply - see that link above again.
How was the computer stored when it was not beeing used for 6 months, somewhere warm and dry or stuck in an attic? Mine usually go in the attic sad to say and require some acclimitisation before I can use them again.
First thing I would try would be to open up the case and remove the graphics card, look at the contacts, make sure they are clean and then reseat in back in the socket and try again. You might want to try this for the other cardss. While you have the covers off check that the CPU heatsink fins are not clogged with dust etc.
Let us know how you get on.