All current versions of SonicOS have RC4 disabled by default. If you have an older version of SonicOS installed you may get an error in your browser not allowing access to the interface. To work around this you can access the UI with an older web browser or if your web browser supports it enable RC4 support. (Enabling SSL3 in Internet Explorer will allow access) To resolve this you will need to upgrade the firmware of your device to the latest General Release. You can do so with an older browser or upgrade your firewall in safe mode.