ARIS Express install problem

I am trying to install ARIS Express on Firefox 5.1 and am getting the following exception when i try to upload the tool.

What could the problem be?

com.sun.deploy.net.FailedDownloadException: Unable to load resource: http://download.ariscommunity.com/antlr.jar

at com.sun.deploy.net.DownloadEngine.actionDownload(Unknown Source)

at com.sun.deploy.net.DownloadEngine.getCacheEntry(Unknown Source)

at com.sun.deploy.net.DownloadEngine.getResourceCacheEntry(Unknown Source)

at com.sun.deploy.net.DownloadEngine.getResourceCacheEntry(Unknown Source)

at com.sun.deploy.net.DownloadEngine.getResource(Unknown Source)

at com.sun.javaws.LaunchDownload.downloadJarFiles(Unknown Source)

at com.sun.javaws.LaunchDownload.downloadEagerorAll(Unknown Source)

at com.sun.javaws.Launcher.downloadResources(Unknown Source)

at com.sun.javaws.Launcher.prepareLaunchFile(Unknown Source)

at com.sun.javaws.Launcher.prepareToLaunch(Unknown Source)

at com.sun.javaws.Launcher.launch(Unknown Source)

at com.sun.javaws.Main.launchApp(Unknown Source)

at com.sun.javaws.Main.continueInSecureThread(Unknown Source)

at com.sun.javaws.Main$1.run(Unknown Source)

at java.lang.Thread.run(Unknown Source)