Admin Lucas,
I'm sure most of us already click on the confirmed link when we joined the site at the beginning. Unless there is another email, i don't know what it is about.
I'm very sure i did click the confirmation links when i first signed up, but does not seem so on the withdraw page, because i still see the "instant is only available to confirmed accounts" msg. I have both the original emails, dated to the day i signed up.
I think you need to put up a notice on the main site, lots of users must be wondering why they can't withdraw, when people freak out, they will just leave.