I'm having the same problem. Sometimes it will verify it, and other times it just won't... I ran in to this problem with a different ASP CAPTCHA code verifier that I was using first, I wasn't sure if it was just me entering incorrect digits at first, but I didn't like it because it was too hard to read any of the 8 digit codes. So I found this WebWizard Capcha and found the images where very easy to make out. This time I know i'm enetering the correct image text. I even disabled the Case Sensitive
to make sure.
Just thought of something, I'm wondering if it has something to do with it setting the blnCAPTCHAcodeCorrect to false when you miss type it and it stays false even when you refresh the image or page.
I'll have to do some more tests. I'll check back in with any results if i find out any information.