Hmm, the only time that error is triggered is if it can't write to the config file. There must be some type of permission problem that's keeping it from passing that step. Try this, line 100 of the install/createtable.php script looks like this:

$fd = @fopen("{$config['FULL_PATH']}/includes/config.inc.php","w");

Change that, to this and it should give the actual problem:

$fd = fopen("{$config['FULL_PATH']}/includes/config.inc.php","w");