My 8310 has a 'fax' symbol in the upper left of the main display. This has been there ever since I received a number of unusual SMS's - a collegue was 'playing' with their new phone
Screenshot available here: http://members.tripod.com/~dr_nico/8310-fax.jpg
Any thoughts..? It's not affecting me using the phone, it's just annoying that I can't get rid of it..!