This is a general rule and you should always take a backup first.

Clear cache files in:
JOOMLA_ROOT/cache/
Clear everything except the "index.html" file. This is just a blank file that causes a blank white screen if someone visits this directory instead of allowing them to see the individual files and directories.

DONE THIS

Clear cached style files:
These are the generated files that usually have random character names.
JOOMLA_ROOT/templates/MY_TEMPLATE/css/
JOOMLA_ROOT/templates/MY_TEMPLATE/css-compiled/
JOOMLA_ROOT/templates/MY_TEMPLATE/js/

NO CSS-COMPLIED AND NOO RANDOM CHARACTER NAMES IN THE OTHER TWO FILES

These vary depending on your cache settings and whether or not you're using RokGZipper or not, but these are the directories you'd check.


Aside from that, there is no guarantee that changing the PHP setting to 5.3 means it is actually running 5.3. If you can create a new install in a subdirectory of the one you are having trouble with, that will let you test if Joomla can run there and you'll be able to see your PHP settings there as well.

CREATED NEW SUB DIRECTORY NAMED JOOMLA TEST FOLDER IN PUBLIC.HTML (THIS IS WHERE THE PROBLEM SITE IS - DOWNLOADED JOOMLA 3 AND UNPACKED INTO THE NEW FOLDER

As for uploading a new version of the Joomla files, the best way to go about doing it is to create a new install so you know all files will be fully installed and created and in the right place, the copy all of those files over EXCEPT the "configuration.php" file.

All other should override and just fine. And just to be clear, I'm referring to core Joomla install, not a RocketLauncher. If you use a RocketLauncher for this, you may override customizations you've done in the template or extensions. Joomla updates are typically just overwriting the files they've patched, so this is sort of a reset on your install and a way to just make sure the files are correct. I'd try using the version you had installed first.