For about a week now I have been experiencing a 403 error on both subdomains of my site. If I click on a referring link in google/twitter/bing/topsy, etc. I get a 403 Forbidden error. However, if I enter the same link directly it works fine. This is happening across mobile and desktop versions and OS'. At first I thought it might be a problem with CloudFlare or W3TC so I tried turning those off but it didn't solve the issue. I have also been looking at htaccess files (root and 2 x subs) and permission settings but no luck. Google webmaster tools doesn't show any issues with DNS, crawling, connectivity, etc. My site isn't on any black lists. Pingdom check tools work OK. The only major chance I can think of was a recent upgrade to PHP 5.3 from 5.2.17. I am working with my host provider to try a manual rollback to the previous version. Has anyone else seen this kind of problem or have any suggestions for things to try to troubleshoot this issue? Thank you.
"Forbidden You don't have permission to access / on this server.
Apache/2.2.22 Server at ja.vstlife.com Port 80"