I notice when switching between 10.1 release and 10.1 stable that mouse sensitivity (for small movements) has changed somehow.
I think the acceleration for small movements is now too fast / non-existent.
stable/10 - r281836
I have a G400s mouse with a high dpi.
Please let me know what information I can provide to give better debug output.
Closing this. This was totally hardware related.
The + and - on the G400S toggle the speed / sensitivity was the issue. I used another usb mouse and fixed the button in the G400s and both work as intended.