I leave my machine on for long periods of time with all windows open. I logged on this morning and found that WU had reboot my machine while ST2 was running in the background.
When I start ST2, I get the error message: "Error trying to parse settings: No data in C:...\Sublime Text 2\Packages\User\C++.sublime-settings:1:1". Looking at the file in question, it is indeed there and empty. Pressing OK to continue, ST2 fails to launch and the executable sits in the background taking no CPU until I end the process manually.
Looking at the workspace I had open, that file is only referenced in "file_history", so it looks like I didn't have it open when ST2 got shutdown.
Deleting the file gets me working again after I restore the C++ settings I had specified. So I suppose there's two bugs in all that: ST2 can't start and hangs if a settings file can't be parsed (I get the same issue with other packages), and for some reason my settings file got blitzed after a WU reboot (although that may just be coincidence).