Appears to download application then quits without an error message. When clicking on the .jnlp file again, nothing happens. I can go into java preferences and remove the application from the cache, but it does the same thing, redownloads the application then doesn't open it.
After doing some research, I found a plugin for Google Chrome that will put current page you are on into an Internet Explorer wrapper with Java 6 installed in it. Its called Rndr and I have tested it on OSX 10.8 and 10.6.8 and it appears to launch any java plugin or .jnlp webstart app in the browser itself.