'cannot modify header info' warning on membership plugin account page update

Hi,

When I try to update my password on the account page of my membership plugin site I get a long list of warning messages, the password is successfully changed but I am then logged out after. This only happens on my live site, not the test site.

Warning: Cannot modify header information - headers already sent by (output started at /homepages/3/d377176883/htdocs/wp-content/themes/theme1322/header.php:2) in /homepages/3/d377176883/htdocs/wp-includes/pluggable.php on line 754

Warning: Cannot modify header information - headers already sent by (output started at /homepages/3/d377176883/htdocs/wp-content/themes/theme1322/header.php:2) in /homepages/3/d377176883/htdocs/wp-includes/pluggable.php on line 755

etc etc

Updating the other fields is fine, this only affects updating the password

i am using membership 2.1.3 and wp 3.3.0

Thanks,

Al