Change default "open with" for Documents directory
Solution 1:
If you have trouble opening any folder and therefor can not use "RightClick (Documents) > Open With Other Application... > File Browser" you can use this from command line
mimeopen -d ~/Downloads/
You will get a choice of options that are related to directories. Nautilus will be #1 in this list:
Please choose a default application for files of type inode/directory 1) Open Folder (nautilus-folder-handler) 2) Other...
Make sure it says inode/directory and not inode/mount!
After choosing 1 all folders will be opened by Nautilus.
Ofcourse this list will have more options when you have more filemanagers have installed.
Solution 2:
RightClick (Documents) > Open With Other Application... > File Browser
http://ubuntuforums.org/showthread.php?t=1702576 << this may be helpful too