System Information
OS X Yosemite 10.10.3 Graphics Card NViDIA GeForce GTX 780M 4096 MB
iMac 27 ince 3.5 GHZ Intel Core i7
Memory 32GB 1600MXZ DDR3
Blender Version
Broken: (Latest 2.74)
Worked: (optional)
Short description of error
Exact steps for others to reproduce the error
Its been like this for last 3-4 versions where when I use blender my whole screens start looking garbled scrambled especially when rendering not just on software but entire screen. Only way to get rid of it is restart computer when I finish with Blender. If Blender is open it will continue.

