I'm having the exact same problem on our assist station (MacPro 2 x 2.66 dual-core, 5gig RAM, 10.5.5, all updates). It installed no problem on our edit station (newer 2 x 2.8 quad, 10gigs, same OS)... same system configs on both machines!
Any help would REALLY be appreciated!
From the "details" button:
com.sun.deploy.net.FailedDownloadException: Unable to load resource:
http://mediaserver.local/~fcsvr/webstart/macJnlp.php
at com.sun.deploy.net.DownloadEngine.actionDownload(DownloadEngine.java:961)
at com.sun.deploy.net.DownloadEngine.getCacheEntry(DownloadEngine.java:1059)
at com.sun.deploy.net.DownloadEngine.getResourceCacheEntry(DownloadEngine.java:113 4)
at com.sun.deploy.net.DownloadEngine.getResourceCacheEntry(DownloadEngine.java:106 8)
at com.sun.deploy.net.DownloadEngine.getResource(DownloadEngine.java:142)
at com.sun.deploy.net.DownloadEngine.getResource(DownloadEngine.java:127)
at com.sun.javaws.Launcher.updateFinalLaunchDesc(Launcher.java:245)
at com.sun.javaws.Launcher.prepareToLaunch(Launcher.java:127)
at com.sun.javaws.Launcher.launch(Launcher.java:95)
at com.sun.javaws.Main.launchApp(Main.java:305)
at com.sun.javaws.Main.continueInSecureThread(Main.java:213)
at com.sun.javaws.Main$1.run(Main.java:108)
at java.lang.Thread.run(Thread.java:613)