radio button validation

[eluser]ommy[/eluser]
for some reason i wasn't getting the right response from the validation class.
I got it to work but i'm still wondering what my mistake was.
Form validation has this knack of bugging me every time i use it

this is working:

Code:

<input type="radio" name="voor" value="1" <?=set_radio('voor','1',true)?> />

still registering the radio buttons:

Code:

$this->form_validation->set_rules('voor');

So if anyone would care to enlighten me what i did wrong or could've done wrong in the first place.

Thanks a bunch and sorry for my semi-irrelevant question