I just tested, and the captcha does appear to be broken in such a way that it is impossible to make new accounts.
I sent him a private message. This does not guarantee that he's seen it, but it's the best contact method I have handy.
Message received. Dave or Wes will have a look tomorrow. Other, more reliable method of contacting me: raise a bug report at http://code.google.com/p/lesswrong/issues/list
Things to check in general when this happens (I don't know if any of them are relevant in this particular case):
Is Javascript enabled? Including third-party sites?
Are cookies enabled? Including third-party cookies?
Are you blocking or spoofing the referer?
After turning on scripting, cookies, and referer, open the registration page again, by clicking a link or copypasting the URL rather than by refreshing the page.
A friend recently said
Does anyone know the solution to that?