Mac OS X 10.10.4, AMD 5770
Short description of error
A mesh with certain modifiers (construction ones that draw in edit mode, such as mirror, bevel, array, etc) will draw corrupt when in edit mode with matcaps enabled. Disabling matcaps, going into object mode, or hiding/removing the modifier will remove the issue
Exact steps for others to reproduce the error
The attached .blend contains some mirrored cubes and has matcaps turned on. Load it up and enter edit mode, observe mess.