I got the 3100 replacement but I had the same problem. However, this time I knew I wasn't going to go anywhere so I decided to get the 4700 receiver from another room and swap it. I knew the 4700 worked on the same TV.

I did that and when I put the 3100 receiver to the other TV, the TV signal was jumping and the colour was kinda alternating between black and green. I wasn't getting the same thing on the other TV.

Oh well, I waited long enough for the software to be downloaded. At the end, everything was back to normal. Then I decided to swap the receivers again. 3100 back to the multi-system TV and I now get colour.

Now everybody is happy but not sure why it happened.