Nokia

Has anyone been able to get Mail for Exchange to work properly on an E71x? It worked perfectly for months, now all of a sudden, it stopped sync'ing. If I try and open the program, I just get a blank screen, then eventually it goes back to the main menu on the phone. If I uninstall, then reinstall the program, I can get it to sync until I turn my phone off, then I'm back to where I was before.