Picture Sources List

When I right-click my desktop and select the "Change Desktop Background" item, the dialog comes up as it's supposed to, but there are two entries for my Aperture library. In addition, I've added numerous folders to my sources list, and apparently they are in the list, but they don't show up. When I go to re-add them, a dialog appears saying that there is already an entry for this folder. How can I fix this? I don't know how this happened.

Not at home now (stuck behind a windows PC at work) but try clicking the arrow, this will reveal more places.

To bypass this problem I usually just do this....

http://omploader.org/vaHox/Picture 1.png

This is what I'm talking about. Clicking on either of the arrows for the Aperture library makes the second one drop down.

This is a known problem? Is there any way to fix it?