Hi Gavin,
I already replied on the other post, the Invalid Session is an Elastix error, not a fop2 error. Remove the index.php, upgrading the Elastix rpm from the fop2 tarball will cause other inconsitsencies as the Elastix rpm version is deeply integrated into Elastix itself (the phonebook is the one from elastix, not the one included in fop2, it requires an open session with elastix and it auto login the fop2 based on elastix credentials, etc..).
But the fix is quite easy, remove the index.php file so the native index.html from fop2 takes over. Regarding Firefox 11, you still need to disable websockets if you connect via https, and when using elastix that is the case. So be sure to set disableWebSocket=true in presence.js
Best regards,