In newer PHP-Versions the count of input-fileds per formula (POST) will be limited to 1000 (unverified information). It seams that this limit is already installed in certain
These changes tend to be well documented. Are you sure that it's been backported to 5.2? Where did you read so? It seems more likely that you are hitting some other limit such as post_max_size or Apache's LimitRequestFields, or even a PHP security mod like Suhosin.
(Furthermore, PHP 5.2 is no longer supported, so I doubt it'd receive such upgrade.)