After I click Begin Installation at step 1b (/install/index.php?install/step/1b) the button goes inactive for a couple seconds then reactivates. A click again and it loads a new page with "Error: You cannot proceed unless all XenForo database tables are removed."
I dropped all tables via PHPMyAdmin and the same thing happens again and again. I have 8 active XF licenses, many on this same machine - never have come across this before.
[Sun Feb 24 00:15:50 2013] [warn] [client] mod_fcgid: read data timeout in 40 seconds, referer: install/index.php?install/step/1b
[Sun Feb 24 00:15:50 2013] [error] [client] Premature end of script headers: index.php, referer:install/index.php?install/step/1b
Timeout of 40 seconds. And seemingly creating some of the tables.
I would see if your hosts would up their maximum execution timeout for PHP. But, at the same time, is there a reason that is so slow? Usually creating the tables takes no more than a few seconds. Is this some sort of shared hosting you're on?