I decided to require new registrations to get permission by me before they can post to the forum. I didn't want to do this b/c I don't want to block valid users. Nonetheless, the site is effectively under attack by spammers and this is necessary.
What I learned is that the spammers are creating their accounts at night, registering as being from the UK, but have IPs from China (they are waking up when we are going to bed). I also see that they are using the similar IP address blocks and I've disabled them.
I also added an RSS feed to my browser of the new posts so I can watch for any spammy posts while I'm at my client's office. This will let me delete the spam and block the spammer immediately.
Hopefully this will slow them down and get this site back to normal without having our wonderful members who volunteer their time on this site having to fight spam rather than helping each other with their questions.
Brian