Drupal is working fine now with PHP 5.2.12. But ISPConfig 3 admin is giving some errors. They don't really affect anything but probably should be addressed.
Strict Standards: ob_start() [function.ob-start]: It is not safe to rely on the system's timezone settings. Please use the date.timezone setting, the TZ environment variable or the date_default_timezone_set() function. In case you used any of those methods and you are still getting this warning, you most likely misspelled the timezone identifier. We selected 'America/Los_Angeles' for 'PST/-8.0/no DST' instead in /usr/local/ispconfig/interface/lib/app.inc.php on line 35
Warning: ob_start() [ref.outcontrol]: output handler 'ob_gzhandler' conflicts with 'zlib output compression' in /usr/local/ispconfig/interface/lib/app.inc.php on line 35
EDIT: It seems zlib compression was enabled after the update and was causing this error. I disabled it and the error went away. Not sure how that happened.