I have set the site's PHP version specifically to PHP 5.3 (which is 5.3.17 to be exact, and shows correctly using a phpinfo() call from the site). The Joomla 3.0.2 install keeps complaining that it needs a PHP version greater than 5.3.1, and refuses to install. 2.5.8 will install fine, but the 3.0.2 fails on the PHP version every time. I have tried with the PHP mode set to CGI, FastCGI both with no success either way. The version check is failing in error for some reason.
This situation is easily repeatable in another website also, so it is not specific to this one site.