Have you tested ram with memtest at all?
http://www.memtest.org/download/5.01/memtest86+-5.01.usb.installer.zip
make a mem pen up and boot from it...just to rule out faulty ram...which can cause all sort of strange things to happen and stop working.....
http://www.memtest.org/download/5.01/memtest86+-5.01.usb.installer.zip
make a mem pen up and boot from it...just to rule out faulty ram...which can cause all sort of strange things to happen and stop working.....