I've only been using C2 for a month now, and I've never experienced this, but then again, I never tried loading.
So, when I run the game for a test, its all good, but when I press L to load it, it says all this junk :
Javascript error! Uncaught TypeError: Cannot read property 'type' of null http://localhost:50000/preview.js, line 5521 (col 18)This may be a bug in Construct 2 or a third party plugin or behavior - please report it to the developer following the bug report guidelines. Subsequent errors will be logged to the console.