Unity 4.3 editor gets permanently messed up if you change code while game is running

If I accidentally change some code and save it in monodevelop w$$anonymous$$le the game is running in the editor sometimes the editor crashes but sometimes I end up getting a permanent error that always shows up from then on and that I can never get rid off even if I undo the changes I made.
In t$$anonymous$$s scenario I get these 2 errors everytime I stop the game running after playing it in the editor..

    Some objects were not cleaned up when closing the scene. (Did you spawn new GameObjects from OnDestroy?)

   !IsPlayingOrAllowExecuteInEditMode ()

I've found the only way to get rid of these is to revert the entire project to the last save where these didnt occur