Error in Captcha

[Peacock1]

Very good at all , I have a problem with my forum. When you finish registering the captcha it is left blank and pictures out letters to complete the registration . Anyone know how I can fix this error? But since you can not register anyone.

Here the image of the error:

[Illori]

http://wiki.simplemachines.org/smf/Visual_verification_code_-_It_doesn%27t_work._What_should_I_do