Check your PHP version and Apache version, I am stuck on the same thing, this is what I know so far, it seems that PHP 4.2.2 and Apache 2.0 have a conflict.
look at this
I still havent solved it, since I dont have a way of upgrading the PHP version.
If you know a quick fix, please let me know.
Please see the thread at http://bugs.php.net/bug.php?id=18648 the problem is (as described by firstname.lastname@example.org) because /etc/httpd/conf.d/php.conf has 2 filters <Files *.php> SetOutputFilter PHP SetInputFilter PHP LimitRequestBody 524288 </Files> replace above lines with AddType application/x-httpd-php .php solved the problem for me
I had to reload PHP and Apache to a later version, it is a fatal combination of PHP 4.2.2 and Apache 2.0.X .
Unfortunately it is the default that is supplied with RedHat 9.
I had to upgrade to Red Hat Enterprise which solved the problem.