Problem solved: After looking at the logs the ModSecurity was using a regex that picked up on some text on the site, changed the text slightly and everything now works. Thanks for the help.
I have Apache(2.2.17) and PHP(5.2.14) running on Linux and I am getting a 403 forbidden error when trying to access a specific php page.
I have two pages, form1.php which passes info to form2.php When I press submit on form1.php I get the 403 error, but if I tried to load form2.php directly by it's URL then it loads fine.
Both pages used to work fine until last week. I know for a fact that the code in the php files hasn't changed(I have re-uploaded to make sure), and am fairly sure that the server software hasn't been changed. All the other php pages on the server have continued working as normal, even the ones in the same directory.
All files in question have permissions set as 644, -rw-r--r-- There are no errors in the Apache logs.
Can anyone suggest anything? This is becoming increasingly frustrating.