Help! Headerfaults everywhere

After upgrading to WP 2.8.4 (I think) there is something terrible wrong. Everything I try (new post, activate plug-ins, export my posts) reslults in ‘header already sent’ faults. I have done all you suggested to restore the wp-config.php but I can’t find the fault. Now, it’s going worse and worse.

Mac OS X 10.6.1