RE: Problem with two modules interfacing
Well, for the life of me I cannot find any info for that reciever except some russian, italian, and german sites, and even then, no pics.
Ideally, unless you want to switch to a discrete screen to see the GUI, which should be an overlay anyway, run all video from one lead. The gui shouldn't just conk out without some additional failure that you would most likely notice. Also, if there isn't a dedicated rca output than video would have to go through the monitor out (or w/e your might be called) connection.
In some cases it is possible that if the gui is an option, the receiver may have reset and you may have to switch it on again. If the gui is the ONLY interface, that is unlikely.
without seeing pics or seeing a connection schematic, it's tough to diagnose. Worst case scenario, you disconnect everything and start with a single video input to your TV to establish the menu and build from there.