Upgrading from a few years old Ubuntu GNU/Linux version to the latest Ubuntu 12.10 might hurt your eyes… that is, if you happen to code in Java, develop Swing applications, or sometimes prefer IDEs such as NetBeans to Emacs. Somehow upgrading to the latest version of Ubuntu creates a problem with fonts and in many Java applications you see very ugly, bold fonts in menus, tree labels, etc.
This has been confirmed as a bug, and you can read more details at https://bugs.launchpad.net/ubuntu/+source/openjdk-7/+bug/937200 or https://netbeans.org/bugzilla/show_bug.cgi?id=221778
Apparently this bug seems to be somehow related to Wine and a font package. The solution that worked for me was simply to issue the following command:
sudo apt-get remove fonts-unfonts-core
Well, I did not need Korean TrueType fonts anyway.