Start fresh ide. Mount following Test and openide.jar. Open the Test.java in
editor. Compile it and execure using internal execution. After the Test is
finished, check mounted filesystems. One is unmounted. Now it seems like Solaris
issue only. If reproduced on other platforms, updates will be aded.

TestCase:

public class Test {
    public static void main(String args[]) throws Exception {
        org.openide.filesystems.Repository rep =
org.openide.TopManager.getDefault().getRepository();
        org.openide.filesystems.JarFileSystem jfs = new
org.openide.filesystems.JarFileSystem();
        jfs.setJarFile(new
java.io.File("/export/home/LastNB/netbeans/modules/text.jar"));
        System.out.println(jfs + "    Valid: " + jfs.isValid());
        if (rep.findFileSystem(jfs.getSystemName()) == null) {
            System.out.println("mounting allowed");
            rep.addFileSystem(jfs);
        } else {
            System.out.println("mounting NOT allowed");
            org.openide.TopManager.getDefault().notify(new
org.openide.NotifyDescriptor("JAR already mounted!",
                                                       
"Error",org.openide.NotifyDescriptor.OK_CANCEL_OPTION,0,
                                                        new
Object[]{org.openide.NotifyDescriptor.OK_OPTION},""));
        }
        System.out.println(jfs + "    Valid: " + jfs.isValid());
    }
}