Small PHP file upload size - FIX?

I have 3 Joomla sites on the same shared hosting account. In 2 of them, when I go to "warning" section under extension manager, i see this error:

"Small PHP file upload size"

I have checked the php.ini file for each of the installation, located in the root folder for each site and the limit is set to 64M. Also, I doubt it can be a host's problem, because 1 of the 3 sites doesnt show the error, while the other 2 do. What could possibly be the reason? Am I looking at the wrong php.ini file?

On all 3 sites, I am also getting the "The PHP temporary directory is not set" . Is this something I should worry about?

I have just updated from 1.7 to 2.5, very smoothly using the extensions manager.

As per my original post, it doesnt sound like a host problem, because I do not get this error on my other site, hosted on the same host and the same shared hosting account.
open your /public_html/administrator/php.ini file. (If there isn't one, you'll need to create one.) Add two lines to that file:
upload_max_filesize = 20M
post_max_size = 20M

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