According to http://java.sun.com/javase/6/webnotes/6u17.html, u17 fixes "6815780 java classes_2d TrueType font parsing crash when stressing Sun Bug 6751322 test case"
This issue has been addressed in following products: Extras for RHEL 4 Extras for Red Hat Enterprise Linux 5 Via RHSA-2009:1560 https://rhn.redhat.com/errata/RHSA-2009-1560.html