404 error on saving a page in processwire

[naruttam]

The Processwire version is ProcessWire 2.4.0 © 2015

When attempting to save edits to the page, instead of getting the pw success message, I get the 404 page not found page.  
This page in question cannot be deleted, moved, edited...nada.
Page edit takes me to: http://www.mydomain....e/edit/?id=5772
When I attempt to save the edits the address bar still says:
http://www.mydomain....e/edit/?id=5772 but it displays the 404 Page Not Found page and changes are not saved.

Also disabled Modsecurity on the server. Any ideas please

[cstevensjr]

What is your PHP version? 

If your hosting environment can support it, you should seriously consider updating your ProcessWire version.  The current stable version is 2.6.1 and it incorporates many outstanding new features/capabilities.