Can't access Admin page after moving to new server

Hey everyone - Happy Thursday.

I'm a little baffled here. I moved the site from one hosting server to another one and I can access the admin page, but it won't process the authentication to get in.

URL was staying exactly the same, database name is different as is the username and password and the path for the root docs... however I changed all that in the header.inc.php and I've done this before without a problem. I just can't figure out what I'm overlooking here. 

Here's what I've checked:

• Everything is correct with the header.inc.php
• .htaccess files are fine
• php5.ini is fine
• the correct version of PHP is running
• cache has all been manually cleared (because I can't get into the admin interface)
• cron jobs appear to be configured and running fine

Here is exactly what happens when I try to access the admin page:

• I login to the site > I click on the admin interface (or type it manually) > somehow it redirects to a slightly different version of the site (instead of https://mysite.com it tries to go to https://www.mysite.com, which technically should work fine anyway) > It doesn't process the session that is already logged in and if I try logging in at the admin page it doesn't process it at all. 
• I have tried looking through every single line of code in the site for the https://www.mysite.com and through the database for it and can't find it anywhere. So I don't know where it's getting that from or if it's even relevant.

I'm at loss. Any ideas?

Oddly Admin is sometimes easier to access than the site itself.

If you can access the site, can you access admin via the spanner, or is that what you mean?

Dumb question: Have you tried accessing admin via it's own URL link: mysite.com/administration?

Have you cleared your browser cache's and cookies because they may be trying to load the old site?

Hello drakemaster!

As johnk42 asked the good list of questions (thnx!) may you please also specify what URL has the $site['url'] variable in your inc/header.inc.php? With or without WWW?

put this in your .htaccess file. It will force all requests for 222 to use non www

#Force non-www:
RewriteEngine on
RewriteCond %{HTTP_HOST} ^www\.example\.com [NC]
RewriteRule ^(.*)$ http://example.com/$1 [L,R=301]

Thank you, everyone, for your help. For some reason, none of it was working. I ended up recopying my site from the original location and then it worked. Must have been some corruption somewhere.