I think you need to get some background images/color involved, there is too much white space, it would help separate things a bit, maybe a background for your navigation other than white, then another for your sidebar, i would stick to lighter and paler colors though.
I quite like it. Looks clean and tidy, with just the right amount of white space IMHO. One thing to remember is: white space is good but white space doesn’t always have to be white. Maybe try experimenting with light background colours or images to pull the whole design together.