Peter,
I’m sorry you had trouble registering; I just tried a minute ago and it worked on my first attempt. I’ve tried to refresh the page a few times and the captcha seems fine to me, but I’m going to get a more detailed look at it shortly.
We did have an issue with the captcha a few months ago when it was serving up greek characters (theta, beta, etc.). This issue should have been resolved. Did you see any of these or was it just the roman script?