While logged in as an admin user, bring up the following on your forums:
ubbthreads.php?ubb=captcha&t=im&test=1
That should give some type of information if it's encountering an error of some sorts.
I'm using GD2 and after re-install my files the captcha is not working any more. I just did a re-install for all files, nothing else changed on my 7.3.1 version.
I run Rick's code and got this:
PHP error: sh: /www/forum/images/captcha/backgrounds/background2.jpg: Permission denied
if I hit reload, got this:
PHP error: sh: /www/forum/images/captcha/backgrounds/background1.jpg: Permission denied
I play with those files permission, and if I give 777 it gave a diff. error:
PHP error: sh: /www/forum/images/captcha/backgrounds/background1.jpg: cannot execute binary file
any other comments please?