It's only just come to my attention, after a recent upgrade to 2.0.16 (latest release).

Users are able to register, when all details are correct, however it seems if the disclaimer check is not checked, or the passwords don't match, or if the username is already taken, then a white page is presented.

There are no errors with php debug or smarty debug.

Cache has also been cleared.

I did a search of XOOPS both on-site and via google, and couldn't find a solution

OK, seem to have fixed it, for anyone else experience similar problems.

If you've ever used a custom system_redirect.html system template, which is sometimes packaged with a theme, then this could be the cause. To fix it, simply download your default system_redirect.html template and then re-upload this one into your custom.

Or of course modify the default template to your needs, then re-upload it to your custom templates.