i have just commented out the lines refering to captcha php on my site because new users could see it but it was always wrong this problem is occuring on xoops2.3.2 with user profile active on php5 and MySQL 5

these are the lines in xoops_root_path/modules/profile/register.php I had to comment out

/* xoops_load("captcha");
* $xoopsCaptcha = XoopsCaptcha::getInstance();
* if (! $xoopsCaptcha->verify() ) {
* $stop .= $xoopsCaptcha->getMessage();
* }*/

When the characters are displayed, there should be no problem to enter the code correctly.
Most problems with captcha are that due to a missing PHP library the code is not showed at all.

Thanks this helped me with the same problem!