On my new wordpress site when I try to insert some php code (template tag, what have you) somewhere between the submitting of the post and the display of the post a space is inserted between the < and the ?. This breaks the tag, and the text of the tag is shown instead of its effect. Using Safari 2 and Firefox, with wordpress installed on a Raq linux system and on Mac OS X 10.4 (Tiger).
An example would be <?php the_ID(); ?> turns into
< ?php the_ID(); ?>