|Possibly bad RAM but there are other things to consider before rushing out and spending money unnecessarily.|
First thing to do is to take of the cover and re-insert the RAM. Take it out and give the contacts a rub with a pencil eraser. This will get rid of any oxides that have formed on the contacts. Re-insert the RAM making sure it is properly seated in its slots.
While you are there check all other connection, especially those going to the hard disks and optical drives. They can sometimes work lose. Makes sure that every cable that is plugged in is still plugged in fully and try again.