What did you do to cause this? If you activate seo urls but missing the htaccess it will render the site useless.
What page were you on? All but the front page.
Describe the defect: 404.
Solution: Run a check to see if the htaccess file exists, if not return a message or ignore seo urls. The latter would be useful.
See this forum thread: http://traqproject.org/forum/showthread.php?tid=228