It's a problem with the font.properties file that Java uses. There's a revised file which you can download and replace the old one with. Check out the font properties section of the Java release notes at:

http://java.sun.com/j2se/1.3/relnotes.html

To learn more about Linux it's probably best to borrow a book from the library or buy a book on Linux. You can also try some general Linux help and documentation sites such as:

http://www.linuxnewbie.org
http://www.linux.org
http://www.linuxdoc.org
http://www.linux.com
http://www.redhat.com (Or the site of whichever distro you use)

You can also read the comp.os.linux newsgroups. There are heaps of ways to find out more! :)