When editing documents, sometimes seemingly randomly, I all of a sudden can't change the format of text before I've written it.
I know that isn't very clear, so here's an example:

I'm typing, and want to make the next word Italic. So I hit Ctrl+I, and type the word. However, the word comes out not being Italic. If I watch while I do this, the cursor blinks twice italic, and then reverts back to normal. Similarly, the button on the task bar goes yellow (as if I clicked it) and then just goes back to normal. The same occurs if I click the button, or if I go into Format -> Font, and make it Italic. This also occurs with Bold, Underline, etc.

If I go back and select the word, I can make it do whatever I like, but obviously this is not ideal.

This seems to happen with certain documents and not with others, so I created a new document, and everything was going well, and then all of a sudden it started doing it again.

Many thanks!