I think I have found a stable solution on my Toshiba Z35:
Get the latest Proset (17.0.0) and Bluetooth (3.1.1311) software.
But, that was not enough.
Then delete your mouse and re-pair it. I did that by clicking the bluetooth icon on the taskbar which took me to the Start Screen version of Settings. (I had previously gone directly to Desktop control panel. Don't know if that matters, but ....)
Good luck.