The newt.jnlp that can be found here http://jogamp.org/deployment/jogamp-next/ has broken links inside. There is no "newt.x11.jar" it must be "newt.os.x11.jar".
Was already fixed: commit c95bc87835319758c10f56ea2cd12093efc3c9c0 Author: Sven Gothel <sgothel@jausoft.com> Date: Wed Dec 15 02:56:37 2010 +0100 Fix jnlp files jar names and removed main attribute of jar ref <module>.[win|x11|osx].jar -> <module>.os.[win|x11|osx].jar nativewindow.os.windows.jar -> nativewindow.os.win.jar newt.broadcomegl.jar -> newt.hw.broadcomegl.jar newt.intelgdl.jar -> newt.hw.intelgdl.jar removed non existing jnlp file for config gl2es12.