I am having the same issue (Windows 7, desktop application). I did not see a resolution on this thread. Can anyone help me? I did find that it is only occurring in the one note. Works fine in any other note, and copying all text into new note allows it to work fine. Would still like to know resolution. It is possible that I accidentally pressed several different unknown keys when it started happening.
+1 Please give the ability to have a black background colour with wite lettering. Much easiwer on the eyes, especially when using it all day.