Comment 27 for bug 118983

Until 6u10 becomes available, a temporary workaround may be openjdk:

sudo aptitude install openjdk-6-jre
sudo update-alternatives --config java

and select openjdk.

For me, this appears to fix the grey dialog box problem, but fonts are rendered differently, which looks weird.

To have Netbeans use the openjdk instead of Sun's Java, I had to edit /etc/netbeans.conf and modify the line

netbeans_jdkhome="/usr/lib/jvm/java-6-sun"

into

netbeans_jdkhome="/usr/lib/jvm/java-6-openjdk"