I have this issue at seemingly random intervals too - Mine is CTRL + Q...
I haven't isolated exactly when it occurs, but I do plugin development and reload files a lot. Sometimes relaunching Sublime Text fixes it, other times it doesn't. It may or may not be related to a typo or bug in an addon.
What addons do you have installed?
When you launch Sublime Text, if you open the console, do you see any errors?
Can you post your console?
To open the console, at the bottom left of statusbar ( Menu > View > Show Statusbar ) click the little application icon and choose Console.