Line 30 of include/functions_install.php is causing an error that is being blocked by an @ on most PDO installations. See this error: http://swiss.ubuntuforums.org/showthread.php?t=1312122. It's occurring on my CentOS box as well. "pecl upgrade pdo" is saying it's the latest version, but PDO_SQLITE seems to think otherwise.
Regardless, this is resulting in PDO-enabled configurations exiting out the phpbb installer with a blank page. Not exactly desirable configuration.
I suggest getting rid of the @'s and handling them otherwise.