As good as I find the SP4 in general, there is one thing that again and again drives me nuts within seconds: This darn things again and again "looses" the mouse (or actually: all its mice). I.e. in the midst of doing something suddenly the mouse (Arc Touch BT Mouse) does not react any more. Same with the Surface trackpad in the attached keyboard. The keys work, but the trackpad is "dead" i.e. one can't move the arrow. This is so infuriating and ridiculous! There I sit in front of a device that has cost me more than $2500 and I can't even move the mouse! This state always takes about 1/2 minute and then suddenly things are back to normal. I assume that the mouse driver has some issue and that there is some timeout before it gets automatically restarted. I kept running task manager for a while, but there seems no unusual activity during these mouse-freeze periods. Anybody having the same issues? Any known cure for this?