I was just going through the nifty-gui tutorials.
There is difference in the tutorials for the one over wiki page and the one that came bundled with my Jmonkey3.0 RC2 copy.
[java]<nifty xmlns=“http://nifty-gui.sourceforge.net/nifty-1.3.xsd”
xmlns:xsi=“http://www.w3.org/2001/XMLSchema-instance”
xsi:schemaLocation=“http://nifty-gui.sourceforge.net/nifty-1.3.xsd http://nifty-gui.sourceforge.net/nifty-1.3.xsd”>[/java]
is the correct code found over the site wiki page
and
[java]<?xml version=“1.0” encoding=“UTF-8”?>
<nifty xmlns=“http://nifty-gui.sourceforge.net/nifty.xsd” xmlns:xsi=“http://www.w3.org/2001/XMLSchema-instance”
xsi:schemaLocation=“http://nifty-gui.sourceforge.net/nifty.xsd http://nifty-gui.sourceforge.net/nifty.xsd”>[/java]
and this is the one that came bundled
I guess the wiki got updated after the nifty 1.3 update
And the stable 3.0 rc2 released before the update.
Anyways,thought just to inform the core members(as they use the nightly and may not be quite updated with new errors poping out of the stable release)
And sorry if i’m just over-reacting 
In short it should be nifty-1.3.xsd in places where it is only nifty.xsd
“Interface/tutorial/step2/…”
is also not available in the jme-test data library.
i also searched for it maually but couldn’t find it.