Common issues with downloading/launching Java Webstart apps:
- Antivirus/firewall prevents download, either completely or typically freezing when the progress bar is nearing the end. Especially common with AVG and McAfee. Fix: whitelist javaws.exe + javaw.exe, turn off file transfer inspection. Some users have reported having to uninstall the antivirus completely before the issue would go away.
- Wrong proxy settings: http://www.java.com/en/download/help/proxy_setup.xml (use direct connection if you don't need proxy)
- Error message "Splash: recv failed": Often caused by Comodo firewall. Fix: you must add javaws.exe to trusted applications in Comodo firewall, see http://geekdrop.com/content/java-web-start-splash-recv-failed-fix . Could also be caused by wrong proxy settings, see above.
- "MalformedURLException: unknown protocol: socket", bad proxy, see above.