Bododio - Sony has a feature that works via HDMI so that when you turn on a device like an STB or DVD it will auto turn on the TV. You want to make sure that is turned off on the tv.

Also, the STB will not let you set to widescreen if the HDMI is not compatible or "clear". To make sure the HDMI detector in the STB is clear do a pull the plug reboot.

While you ar not using HDMI, the problems you are having can be caused by HDMI process within the two devices.