/usr/local/fop2/fop2_server -v

fop2_server version 2.26

I've cleared cache and restarted the server and continued the same problem in firefox11 ....
only when it is disabled the webSocket in presence.js file that works in firefox11.

Nicolas,

I update to version 2.26 now and had the same problem in firefox 11.
Only disabling websocket it worked.