Comment 8 for bug 511656

ok so by default rgba is enabled

to change that edit in gconf-editor the following key: apps/nautilus/preferences/rgba_colormap
this way you enable or disable the rgba support...by disabling it you should retrieve the compiz menu shadows.

If you know a better solution than this switch let me know, there's some problems with rgba, it's the best i can do for now.
Tell me if it work as expected.