If it's the site in your sig (which wrongly has a hyphen in the name), then the captcha is working ok as I just filled it in and it only told me the rest of the info on the page had not been completed.
However, that captcha was beaten a long time ago by the bots so it's not worth trying to get it working. Go straight for the Q&A code.
How to configure Q&A
- Administration Control Panel (ACP) > Spambot countermeasures> Installed plugins > click the dropdown box and select Q&A (it will be greyed out)
- Click the configure button then click add
- Add your question and answer (you need a Q&A for each language you have installed) click submit
- Click "back to previous page" then click "back"
- Select Q&A from the dropdown box (again)
- Click submit at the bottom of the page.