Well I don't see any attempts to exploit a vulnerability.
The only curious thing is someone who is hiding their browser name and version is hitting several pages (faq.php, search.php, etc) at the same time. I believe this to be possible be more than one person - they appear to sometimes use Firefox 1.0.7; however most of the time whatever browser they are using (not Firefox) is following links wrong:
The HTML entity should not appear in Apache log. This is most likely a bot or other automated process, like a bad proxy.
Why this would cause a high server load eludes me. There are not 7,000 requests for PHP scripts in the 5 days logs that you sent me, much less a single day. On 2005-10-11, there were 3,363 log entries and only 1,605 had to do with PHP scripts.
Did you install any phpbb mods after you completed the one-click install?
Perl / MySQL / HTML CSS