Thread:Project:Support desk/Error 403 on some pages after upgrade 1.16.5 to 1.17.0

Prior to the upgrade everything was working correctly. Following the upgrade most things are still working but any page in any namespace with a name ending in .js or .css has a problem. I can access the page using the syntax /wiki/Pagename.css but if I use /w/index.php?title=Pagename.css I get a 403 error saying I don't have permission to access /w/index.php on this server. This is very frustrating as I need to update MediaWiki:Common.js! It works fine on any page that doesn't end in .js or .css.

I am using MW 1.17.0, PHP 5.3.6 and MySQL 5.1.56.

Any ideas?