Took me 5 attemps to manage to read the letters.
And that was only registration. Now I have to do that each time I post >:(.
Consider changing your captcha generator.
You only have to do the captcha for (something like) your first 7 posts.
Spam was getting through with an easier captcha, and I would prefer only to allow in users who actually care about what they have to say (enough to beat a few hard captchas) but I suppose I can make it slightly easier.