I read your post, I am currently running four subs. Obviously you have already loaded your first, go back into: Settings : Profiles. Press add, it will auto generate a new Mac code and serial number then you can add your second , third or fourth.
Best depending on how many subs you want to run,to take a screen shot of the numbers and obviously when loading give each one a different name. Then whilst watching one, if it crashes, press menu button , scroll down on setting to : watch tv and as in my case all four subs names come up with the blue dot for highlighting the one I was watching, then choose another provider, press ok, and it will then load into the one you have chosen . Job done!