Captcha always incorrect

Hi – I love this plugin, but I’m having a problem. I just set up the contact form, and am sending myself test messages. But every time I input the Captcha, I get an “Incorrect Captcha!” message. I know I’m inputting them correctly. I even got one test message sent to my email, even when it said the Captcha was incorrect. Is this a bug, or is there something I can do to fix this?

Also, is there any way to change the Captcha Incorrect! message (to something a little more friendly)?

Thanks very much –

http://wordpress.org/extend/plugins/contact-form-with-captcha/