Server 5.0.4 causing issues with apache

Hi I have has an open source asset bank (resource space) running on our server without issue, but since the update to 5.0.4 it has started displaying error text within the pages when I visit the asset bank.

The error is:

HTTP/1.1 200 OKDate: Tue, 13 Oct 2015 15:39:18 GMT Server: Apache X-Powered-By: PHP/5.5.27 Expires: Mon, 26 Jul 1997 05:00:00 GMT Last-Modified: Tue, 13 Oct 2015 15:39:18 GMT Cache-Control: no-store, no-cache, must-revalidate Cache-Control: post-check=0, pre-check=0 MS-Author-Via: DAV Keep-Alive: timeout=15, max=99 Connection: Keep-Alive Transfer-Encoding: chunked Content-Type: text/html; charset=UTF-8 202c

The asset bank loads up correctly to start with but then when you click on any link it slows to a crawl and the page show the error. the rest of the page continues to load as normal eventually but is painfully slow.

If I refresh the page it will often just display the php markup, then another refresh will bring the page back again