Just tried writing one, and it's working fine for me. Occasionally it doesn't seem like anything happens when I press the Submit button (no message or anything) but after a while it's posted anyway. Occasionally I post a review and it doesn't show up until I've refreshed the page a few times. I assume those problems are server-related since they only happen occasionally.
As for not being able to select stars, that's never happened to me. To rate, just hover over the stars and click somewhere, maybe you're pressing down and dragging instead?
Have you tried different browsers? Is it not working in any of them? How about disabling browser plugins?