Win 8.1x64, 3xGTX580
Short description of error
Continuous grab, when panning in a region with middle mouse/wheel press, occasionally (at a rate of about ~10% of events under normal use) produces double overflow when mouse goes out of scrolled region area. Instead of continuous panning by 3px for example, the region jumps 3px+the width or height of the region. As if the mouse was ordered to be relocated by continuous grab, but it's relocation by system got delayed so that it's position outside of the region got registered again.
The behavior is most pronounced when panning in node and graph editors, but sometimes happens in 3D viewport too. Happens at any speed of panning, but probably more frequently at speeds higher than pixel by pixel movement.
Wasn't able to reproduce this on Ubuntu.
Unfortunately there is not much of other correlations noticed, though this has happened for years on Vista and Win 8.1 with different mice and different mice settings.