Hello There,
I have this problem. I created a custom hidden field 'usergroup' to hide/show some field during registration and it works ok.
After I created a second custom field (text field) called 'auth-code' that must appear only when usergroup=professor, and it works.
The problem is that, when usergroup has other values (different kind of user to register), I see at the beginning of the registration a blank screen (because Validation Tab that contains that field is hidden) and I must click on Next button to start the registration process.
How to correct this behaviour ?