TBB breaks Etsy

Etsy does not work in TBB 2.3.25-2 (I assume it doesn't work in any of the previous versions either). To reproduce:

• Go to http://www.etsy.com/
• Click "Sign In"
• Nothing happens

The site is supposed to display a window that allows you to log in. You can get around this by first clicking on "Register" and then "Sign In" (you get a new page, not just a small window on top of the existing page).