I get the below error when saving or publishing a post. I have read the other posts here and the section in the Codex on troubleshooting this and done what is suggested. Nothing works. Interestingly I updated two other sites at the same time. These are on the same host and use the same theme. These sites work fine. Thanks for any help, other than going back to 2.9.2.
Warning: Cannot modify header information - headers already sent by (output started at .... /public_html/wp-includes/post-template.php:54) in .... /public_html/wp-includes/pluggable.php on line 890