Reportedly caused by Ubuntu fontconfig files missing in Java 7 installation. Users who copy the files from Java 6 report the problem disappears.
Ubuntu launchpad bug:
(last comment #44 explains the workaround)
related NetBeans bug:
If this is by design, can you please comment into the Ubuntu launchpad bug what is the reason and what the users need to do on their side if they do not like it? Thanks.