Rational Change Fix Pack 6 (126.96.36.199) for 5.3 was recently made available. This contains all fixes on top of Rational Change 5.3 and includes the fixes from each of the previous 5.3 fix packs. It requires that Rational Synergy Fix Pack 5 (188.8.131.52) be applied to the Synergy installation and databases.
You can get full details about the fix pack, including installation instructions and a download link, go to http://www-01.ibm.com/support/docview.wss?uid=swg24035646.
To see a list of eveything that is fixed by this and previous fix packs, check the fix list at http://www-01.ibm.com/support/docview.wss?uid=swg27021238.