Cannot modify header info

[brimsjewelry]

I get the following when I attempt to update or add a new product:

a
Warning: Cannot modify header information - headers already sent by (output started at /home/xxxx/public_html/admin/includes/modules/update_product.php:1) in /home/xxxx/public_html/admin/includes/functions/general.php on line 34

The product or change of info is recorded and saved but it's a pain to have to back track to get to a usable page. Anyone know how to correct this error?

Thanks

Jason