Im using wp 3.0 phpbb3 3.06 wpu 0.8.5 I have followed the wp3 upgrade code change from wpu here http://www.wp-united.com/2010/06/19/wp-united-v0-8-5-and-earlier-with-wordpress-3-0/
here a page where you can see the two errors below
Warning: require(wp-includes/theme-compat/comments.php) [function.require]: failed to open stream: No such file or directory in /home4/techtro2/public_html/nanostream/wp-includes/comment-template.php on line 893
Fatal error: require() [function.require]: Failed opening required 'wp-includes/theme-compat/comments.php' (include_path='.:/usr/lib64/php:/usr/lib/php:/usr/share/pear') in /home4/techtro2/public_html/nanostream/wp-includes/comment-template.php on line 893
Tell me if you need more info thank you in advance.