I don't think that LP is in the habit of announcing minor version upgrades, or giving you a way to stay back at an older level. I presume you're thinking about the "deprecated functions" warnings you'll get if you use certain PHP functions. You should be able to set a flag controlling warning and error messages to exclude E_DEPRECATED (or something like that). Or, you might just bite the bullet and go through your code replacing various "ereg" family deprecated functions with their "preg" family updates. I'm not sure what to do about "session" functions. Eventually the drupal developers will have to address these deprecated functions, as they will completely disappear in PHP 6.0.

http://us.php.net/manual/en/migration53.deprecated.php
http://forums.oscommerce.com/topic/341737-function-ereg-replace-is-deprecated/page__p__1434612__hl__eregi%20deprecated__fromsearch__1&#entry1447311
http://forums.oscommerce.com/topic/342525-page-script-error/page__p__1430745&#entry1430745

The script
will tell you exactly what level of PHP you're running. 5.2.x is pretty common at LP, so I'm surprised that WP is complaining that you're not at 5.2 or higher. Possibly you think (and even cPanel thinks) you're at PHP 5.x, but really you're still at 4.4.x? Is your server still at base PHP 4, with a button to switch to PHP 5? You may need to switch back to PHP 4 and re-enable PHP 5 to get everything in sync. You don't have any code in your .htaccess to downgrade to PHP 4?