You must have some field(s) in your footer that has something wrong with it.

Place your cursor in the footer;
Do ALT-F9 to toggle field codes;
Select the text in the field (The stuff between the {}) and copy it;
Post that text back here so we can have a look at it;
If you have more than one field, post them all here;
Don't forget to do ALT-F9 to toggle the display of field values back.