when i view source of your page, the image source is not correct
<img src="?noisecolor=000000&bgcolor=ffffff&textcolor=000000&transparent=0&characters=5&width=200&height=40&font=../WA_ValidationToolkit/Fonts/monofont.ttf" alt="security code" />
the image souce for the contact form solution pack should be:
<img src="WA_ValidationToolkit/WAVT_CaptchaSecurityImages.php?noisecolor=<?php echo $WAGLOBAL_Captcha_Noise; ?>&bgcolor=<?php echo $WAGLOBAL_Captcha_BG; ?>&textcolor=<?php echo $WAGLOBAL_Captcha_Text; ?>&transparent=<?php echo $WAGLOBAL_Captcha_BG_transparent; ?>&characters=<?php echo $WAGLOBAL_Captcha_Characters; ?>&width=<?php echo $WAGLOBAL_Captcha_Width; ?>&height=<?php echo $WAGLOBAL_Captcha_Height; ?>&font=<?php echo $WAGLOBAL_Captcha_Font; ?>" alt="security code" />