symfony 1.4.16 has just been released.
Here are the changes from the CHANGELOG:
-  fixed sfChoiceFormat when a string to translate contains a valid range (closes #9973)
-  fixed saving i18n fields in subforms (closes #7626, patch from yoshy71)
-  fixed last modified date calculation in sfMessageSource_Aggregate (closes #9981, patch from jamiel)
-  fixed merging problem for the routing configuration (closes #8348)
-  fixed ob_start() behavior on CLI (closes #9970)
-  fixed ob_start usage (to avoid warning in PHP 5.4, closes #9970)
If you've checked out a copy of the tag from Subversion you can switch to the latest version:
$ svn switch http://svn.symfony-project.com/tags/RELEASE_1_4_16
If you are using the PEAR package you can update using the pear command:
$ pear upgrade symfony/symfony-1.4.16
And as always, don't forget to clear your cache after upgrading.