I am having a similar problem with webstart. I use JDK 1.6.0_20 linux, Netbeans 6.8 for development and Glassfish OSE 3.0.1 (build 18), but I had this problems with earlier builds too.
Webstart complains, that some resource can not be loaded.
Here is the (localized) Exception:
com.sun.deploy.net.FailedDownloadException: Ressource konnte nicht geladen werden:
http://localhost:38634/___JWSappclient/___app/TestEE/TestEEClient.jar
at com.sun.deploy.net.DownloadEngine.actionDownload(DownloadEngine.java:1376)
at com.sun.deploy.net.DownloadEngine.getCacheEntry(DownloadEngine.java:1529)
at com.sun.deploy.net.DownloadEngine.getCacheEntry(DownloadEngine.java:1507)
at com.sun.deploy.net.DownloadEngine.getResourceCacheEntry(DownloadEngine.java:1613)
at com.sun.deploy.net.DownloadEngine.getResourceCacheEntry(DownloadEngine.java:1538)
at com.sun.deploy.net.DownloadEngine.getResource(DownloadEngine.java:217)
at com.sun.javaws.LaunchDownload$DownloadTask.call(LaunchDownload.java:1739)
at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303)
at java.util.concurrent.FutureTask.run(FutureTask.java:138)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
at java.lang.Thread.run(Thread.java:619)
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