Whenever i put ram into the second memory bank my macbook will not start

I've only had one 1GB ram installed while ive had this macbook. Recently when i tried to install a new osx i was told it needed more memory. So i ordered another 1GB ram and installed it into the second memory bank. When i tried to turn on my computer, it sounded like it was ready to start up but then it repeated the process numerous times and all i had was a black screen. I figured the ram i bought just was defective but then i played around with it and took my old one out and put the new one in the first slot and it worked fine. Then i took my old one that worked as well and put it in the second slot while the first was empty and the problem reoccured. What is the problem here and is it fixable?