Hm. Memory coming back a bit... it wasn't specifically during long ethernet transfers. It was something related to temperature.

If the Karma was cold, all was well. Then if I did a long USB transfer (filling the entire player from scratch, let's say), thus warming up the player, then after that if I tried to connect with ethernet, it wouldn't connect at all, the ethernet simply wouldn't work, it failed the initial 10/100 handshaking with the switch. You'd get a "steady" traffic light on the ethernet plug instead of a blinking traffic light.

I could be mixing up two separate problems here in my head, so someone from Rio correct me if I'm wrong...