So far, I'm loving' it AW... no problems like you're having. Did you download the latest software from their support site? I did that as soon as I set it up although I don't know that a difference was made. It really has made the Surface Pro a delight to use for me anyway. Hope your problem resolves!
The biggest problem I am having with the Ultrathin mouse is that sometimes I touch it and the window I am using GOES AWAY!!
Often I have to restart the program and then it comes up right where I left off. It's more than minimizing -- it's like it closed the program but it really doesn't it just goes invisible or something.
Very strange and VERY aggravating.
I don't know if this is a characteristic of the mouse or if it is Logitech's Setpoint software having a bug.