Header error when adding link to post

Hi!

I’ll get the following error when i’m trying to add link to my post:

PHP Warning: Cannot modify header information – headers already sent by (output started at /foo/wp-includes/wp-db.php:160) in /foo/wp-includes/pluggable.php on line 386, referer: http://foo.org/blog/wp-admin/post.php?action=edit&post=34

I checked those files wp-db.php and pluggable.php for errors, according to this help: http://codex.ww.wp.xz.cn/FAQ_Troubleshooting#How_do_I_solve_the_Headers_already_sent_warning_problem.3F

I dont get the following error when i’m trying to make post without link or with attachment. Im using latest version provided by svn