Lagging cursor from magic mouse and magic trackpad

I have a brand new mac mini 2012 connected to a Thunderbolt display. Since the Thunderbolt display was connected, I sometimes get a lagging cursor, meaning that moving the mouse/trackpad leads the cursor to follow the position very slowly. I have connected both, a Magic Mouse and a Magic Trackpad.

I'm trying to track down this issue but up to now, no avail. I've already connected another Magic Mouse, but same here.

Any idea welcome.

EDIT: if only the trackpad or the mouse is attached, it gets a bit better, but still not acceptable. I also moved around my WiFi-station and the Mac mini – not better.