Reset Password not sending the second e-mail

I have searched the forums, and so far I can’t find the answer.

WordPress 1.5.2.

When I user forgets their password, they ask for their lost password, and they enter in their user and e-mail information. An e-mail is successfuly sent informing them that they can reset their password by clicking on a link.

However, when this link is clicked on, the following message appears:

The e-mail could not be sent.
Possible reason: your host may have disabled the mail() function…

Now obviously, the mail() function does work, because they got the first e-mail. I am at a loss at where to look.

Thank you for your help, as always.