I have a Kabel Deutschland cable box (Sagemcom dci85hd KD). I am able to get it to work with my Slingbox 350 by using the receiver "DVR20" under "Kabel Deutschland AG". Works beautifully. The remote looks the same as the one in my living room, all buttons work except the arrow keys (up/down/left/right). When I press an arrow key, the user interfac eon the receiver jumps 2 items instead of 1. Also, the green light on the reciever flashes twice instead of once. I conclude that the Slingbox sends two button presses instead of one. Or the reciever interprets it that way.
I have tried different locations and setups of the IR blaster to rule out any rays bouncing off walls and being counted twice and such. No success.