Sometimes I experienced a problem when typing a text, and couldn't figure out the reason.
The problem was - when you, for example, try to edit a sentence in Word or any other text editor by adding some words inside, and you start to type, the text you are typing replaces the existing text instead of adding words inside the sentence and moving the already existing words forward. (Hop you got what i meen).
Recently I have discovered, that such behaviour starts when you press the INSERT button.
The INSERT button is often near the BACKSPACE button, so, when typing fast, you can ocassionally push INSERT instead of BACKSPACE.
I have noticed that just recently, so, now I know that if the text is being replaced, all I need is to press INSERT one more time. (I always was confused and rebooted before).
Hope this helps for somebody