JS errors on Send Page by Email

Steps to reproduce problem:

-Login as any user you want
-Click on the Send Page by E-mail.
-When filling the To: form, type an existing user name. You will get the auto-complete function.

When clicking on the desired user, js error pops-up.
(Note that users have an e-email address on their user profile)

Also, when clicking on send you also get a js error.

This happens on IE6, IE7.

Screenshot attached