When Dawn enters the kitchen to discover an invisible Buffy, the pizza box on the counter changes places and several new items appear from one shot to another.
When Buffy is talking to Dawn about getting rid of all the magic stuff for Willow, Dawn's hair switches from being over her shoulders to behind them.
When Buffy lifts the "Dawn Summers" folder, her fingers are visible for a moment, even though she is supposed to be invisible.
When Buffy is invisible and harassing the Social Services employee, she moves her coffee mug from the right side of the desk to the left. When she places the mug on the desk, you can see a hand grasping the mug.
When invisible Buffy is typing on the social workers computer, you can see the strings that are moving the keys.
When Buffy pays a visit to Spike in his Crypt the TV can be heard but the screen is blank even before she turns it off.
In the scene where invisible Buffy walks along a road talking to herself, the moving shadow of a boom mic is visible for a few seconds.