For example, I press left click on the 3D view to change my cursor position. Nothing happens until I do something else, for example zooming in/out.
Also, I press 'T' to hide the tools panel. It just does it after doing something else.
In summary, whatever I do, it gets executed/showed up with "one instruction of delay".
SORY if it's a noob question
Update: I tried Blender 2.7 and Blender 2.79. Both on Windows 7 64 bits
Resolved :) Now the behaviour is correct, with these Window Drawing Method configs: Window Draw Method: Full MultiSample: 2 Region Overlap checkd