PHP 5.2.9 changed the default sort flag used from SORT_STRING to SORT_REGULAR, in 5.2.10 changed it back.
Since some distro's seems to have chosen 5.2.9 as version (suse, check if it is patched version for this bug or not) we should maybe workaround this by setting the sort flag manually.

Example:

$array = array_unique( $array, SORT_STRING );

http://php.net/array_unique

Note: make sure SORT_STRING is defined in all supported versions of php, read: 5.1.x.