This Bugzilla instance is a read-only archive of historic NetBeans bug reports. To report a bug in NetBeans please follow the project's instructions for reporting issues.
"Unload" of the previously loaded web-application does not work. It's report that from Ant script that "BUILD SUCCESSFUL" but if you call Off-Card Installer's "list" subcommand manually then you'll see that the module is still on card.
Also highly unlikely to be caused by anything in the IDE.
Instance is probably destroyed - after unload on a web app, it is no longer accessible via a browser. This is probably a duplicate of issue 177997
*** This bug has been marked as a duplicate of bug 177997 ***