I've just installed Netbeans 7.4 with Java7u51 on Ubuntu 12.04 running in VirtualBox, and every time I started Netbeans the sidebar and the menubar from Ubuntu's desktop disappear.
They're still there (if I move the mouse over the place where the icons should be the balloons appear saying which icon is there).
The only thing that I can do to show the bars again is, after closing Netbeans, click on the "Work areas" icon, choose any work area and the bars are redrawn.
What can I do to fix this? It's really annoying...