Since you have had it apart, I would strongly suggest to double check your work. Make sure that the thermal paste is properly applied and that your heatsink makes good contact. Tighten the screws properly and make sure that you have a snug fit. Amazingly enough, there is no information about solid lights. Check on here and see if you can get the secondary error code. It will help you to narrow down your error.

If you don't put the spongy pads back on the four chips underneath the motherboard you will have two rings. If you don't have the pads you can use a rubber brick eraser and cut four pieces about a quarter of an inch of thickness and and tape tem to the chips.