To access your application files using a proxy server, you need to modify configuration file default.cff.
JavaCommand=java -Dhttp.proxyHost= your.proxy.host.com -Dhttp.proxyPort=portnumberFor unmanaged browsers, add:
-Dhttp.proxyHost=your.proxy.host.com -Dhttp.proxyPort=portnumberto the Java invocation line in the VoiceXML 2.0 script. You might want to make a copy of the script instead of editing the original.