I am using Illustrator CS5 and the grey background around the outside of my canvas/page I used to have and loved has gone white. I do not know why. I can not change the colour in preferences-user interface, as this was introduced in CS6. I have tried ticking and unticking the overprint preview and this makes no difference. Any help would be much appreciated. Thank you.
Have you checked this setting?
Edit > Preferences > User Interface
Choose your desired Brightness
Make sure "Match User Interface Brightness" is selected for Canvas Color
Let me know if that helped!