I seem to remember reading on another forum about some folks having the same problem. What it boiled down to was the folks that were having the same problem as yours had changed their theme to something other than the default Ubuntu theme and I don't remember which theme was the culprit. The short fix was to change the theme back to the default theme.
I know the brown seems yucky, at least I thought so at first but now the brown default has grown on me a bit
Hope this helps a little bit Howard.