aertie - If all you bought were the peanut butter (Y-Pb-Pr) cables, all you'll get is video. You have to use either optical or RCA audio cables for your audio hookup.
This is where hooking up a 2nd HDTV to the 722 TV1 location is difficult. The following assumes one of your TVs is in the room with the receiver.
If you want to do this, you'll probably need to use HDMI for the first location (since it brings A/V, thus freeing up options for the audio at the 2nd HDTV), and use component for video + RCA (or optical cable thru digital audio output, though there may be distance issues) for audio at the 2nd HDTV.
Of course, at the end of all this, the 2nd HDTV will still have to watch the same channels as the first. You'll probably want to make TV1 into UHF Pro so you can put separate green UHF Pro remotes in each HDTV room (at least you won't have to carry a remote from room to room). Be sure you watch your remote addressing if you use this option, so your TV2 doesn't end up conflicting.