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.
Now when units are open implicitly, this is not synchronized well enough. Therefore there is a possibility of implicit unit opening o.n.m.c.repository.impl.DelegateRepository synchronizes explicit opening. o.n.m.c.repository.disk.DiskRepositoryManager opens a unit implicitely. This is not synchronized - there is a possibility that the project is being closed in another thread, which would lead to exceptions.
It seems that the particular consequences are recently fixed. That's why I leave it P3.
To the extent that timing/synchronization problems still exist then the underlying issue needs to be fixed. Otherwsie this defect should be closed. I'm escalating to P2 pending that determination and/or code change.
Fixed: http://hg.netbeans.org/main/rev/45ff317b9a66