In the schematic viewer, when I hover over a cell, a box appears with cell information.
When I move the mouse away again, the box disappears, however a pixel gets set to the bottom left of the cursor at this time.
This pixel goes away when the next cell information box is displayed.
I am not sure whether this is a Vivado issue or due to a graphics card/driver issue on my PC.
This is a Vivado visual issue only and is fixed in Vivado 2014.3.