The "Preview" function on private messages appears to be broken - hitting the button just displays the outside PHPbb frames with no message space. Submitting messages appears to function smoothly, but not being able to preview to check spelling, tag formatting and the like is somewhat distressing.
Running Mozilla 1.5 on a WinXP system; the message in question used BBcode formatting tags but no smilies, HTML, embedded images or off-site material.
Noted - will get to in probably about a week (school semester just started - bites into my volunteer time. :-/ )