Buttons: When a button has the mouse go over it, it gets the square around it that makes it look like it is selected. The button does not redraw when the mouse goes away unless it lands on another button.
Example: Buttons 1 - 4 on the task bar and the buttons at the top of the ReactOS Explorer
Typing Cursor: When you type some times when you move the cursor to a different text box an image of the cursor remains in the original text box. This depends on if the cursor is shown when you move to the other box.
Example: 2nd stage ReactOS setup