Version 2.0.x of Gallery added a realpath() test in the
Gallery_utils::CleanFile() method that forces all images and image directories
to be located under ($config['root_path'] . '/' . DEFAULT_GALLERY_PATH). 
Symbolic Links to images or directories elsewhere in the filesystem no longer
work as they did in earlier versions of Gallery.

This is a major inconvenience. It means that images that used to be shared
between different modules must now be duplicated under DEFAULT_GALLERY_PATH. 
This wastes a great deal of disk space and is difficult to maintain as updates
must be synchronized between two different directory hierarchies.

I understand the desire to have things more secure, but this issue may force me
to abandon the Gallery module when I upgrade to CMSMS 2.0.1.  Something I would
rather not do.

One possible solution might be to add a Gallery module method or preference that
would allow one or more additional subdirectory paths, located under
$config['root_path'], to be accepted by the Gallery module, rather than
DEFAULT_GALLERY_PATH alone.  This should allow Symbolic Links to be used again,
within these additional subdirectories, as they were in early versions of
Gallery.

I'm sure that there are other, perhaps simpler, solutions. 

Others Gallery module users have seen this problem, as well: 
http://forum.cmsmadesimple.org/viewtopic.php?f=7&t=70648&hilit=Gallery+symlinks