I had a satellite receiver do the same thing, 3 of the 4 legs turned into a tar like substance. I got some on my hands and it was really hard to remove.
Two of the rubber feet have gone gooey while in storage in my parents' house. It hasn't been in the loft for long, only over the summer really, and before that it was in a comfortable spot in the cupboard. Any ideas why this might have happened?