Session not storing data across functions?

[eluser]fireproofsocks[/eluser]
I'm going nuts... I'm missing something.

This works:

$this->session->set_userdata('email', 'xyz' );
print "email: " . $this->session->userdata('email');

But when I separate the functions by setting the email in one controller, then redirecting to a new controller via header(), the email comes up blank when I try to read it in the 2nd controller function.

What's going on?