Also, I noticed last night in PvP that each time I click a button on AutoBar (to use a Healthstone, in this case) my PC freezes up for a few seconds.
I narrowed this down more specifically. When I mouse over a button and click it, there is no lag. However, if I then click it a second time without first moving the cursor out of that button's mouse over, the UI lags up significantly. This is especially noticeable if you spam click a button (for example when it is about to come out of cooldown) and my perceived fps goes into low single digits.