Sometimes you have to keep trying new things until you find one that works. Depending on what your community is, it can be hard to get people to click with even double those traffic numbers. I have a friend with one of the most popular TV fansites in town but she's shutting down because no one is clicking.
It's not as easy as putting ads on a site and waiting for the check. It may mean putting direct links to items in your posts (Like a book review with a link to that book, or movie.) Try other ad programs, ask people if they even notice the ads. Some don't. Maybe different ad placement will work. Lots of variables, you just have to work at it.