Howdy,
there is some new bot program that is reading the captchas and answering the opt-in mails, sometimes even throwing up a post. I have been getting 2 or 3 a day and up to 10. At least the forum is small enough that I can catch them. I have it down to 3 main ISPs now, cashette.com, mail.ru and gawab.com all spamming one forum which is now invisible. I'm also looking at a new captcha system based on this:
http://www.mshp.dps.mo.gov/CJ38/search.jsp
the forum that is getting hit has the highest google hits.