Hi Paul,
The error you mention is as it says - output was made where it was not expected.
This can happen one of a few ways:
1. Extra line break, space etc. before the opening <?php tag
2. Extra line break, space, etc. after the closing ?> tag.
3. Output from PHP, ie: echo "Example<br>";
4. A PHP error message, although such a message should be displayed before the header warning..
If you continue to have troubles, email me at dean@... with an exact copy of the signup-xtra.php file.
Regards