A Database Error Occurred in codeigniter.
You're getting this error because the folder "/captcha" is either not on your server or has the wrong permissions set.
if the image path doesn't exist, or isn't writeable the create_captcha() function returns false, have a look in the captcha helper.
the column captcha_time in your captcha table cannot be set to null.
you have to sent the time.
as far as i understand: $cap['time'] is actually null or not set.
maybe you missing install php-gd extention.suppose your environment is fedora.yum install php-gd