There are many others having the same problems with memory on that motherboard.
Some say a bios update to 1103 will help.
On guy solved it by setting the memory to 5-5-5-14 and 2.1v in bios
Another set it to 'auto' and 2.2v
Also check this out:
Memory Qualified Vendor List for P5N-E SLI
http://dlcdnet.asus.com/pub/ASUS/mb/...-E_SLI_QVL.pdf
However it MAY be a heat problem caused by not enough power to the fans of you cpu or gpu. If you let it all cool, you should be able to boot again. If not, it's not a heat problem. :-)