I posted this message to the Drupal forums a day and a half ago. I realize it hasn't been that long, but I thought I'd post it here as well, in case someone here has an answer and doesn't read the forums (like myself).
I have installed the 4.6.0 version of the captcha module in the 4.6.3 version of Drupal. I have configured it as the instructions say. I'm only using it for the initial account registration, so I'm not dealing with the comment wierdness. The image shows up and is legible, but no matter what is entered in the text box, it always fails with the following message:
"Please re-recognize the word shown in the image."
At one point while testing, I clicked on the "Create new account" button without entering any text in the captcha box, and it accepted it and the account was created. So it always fails with any text entered in the captcha text box and passes with no text entered.
I've been doing some searching on drupal.org and on the Internet in general, but I have not found anything that addresses this issue. Does anyone have any suggestions as to what might be wrong so I can fix this odd behavior?
Additional note: In my troubleshooting, I've installed the CVS version of the Captcha module and patched it as directed by http://drupal.org/node/24556, and the behavior did not change.