Comment 21 for bug 556670

Funny thing - when Compiz settings in Unity are set like these of Classic-no-effects, the rate of bug occurrence decreases. Now brush freezes after 9-10 strokes.

Namely, I checked these ones in Utility section of Compiz (others should be unset): Bailer, Detection, Regex Matching, Session Management, Compiz Library Toolbox, Mouse position polling.
... in Windows Management section: Place Windows, Grid, Move Window, Resize Window.
... in General, OpenGL unchecked all flags and set Texture Filter to "Best".