Error after upgrade

I just upgraded to 2.3 and keep running into a small error. I keep getting the page where it says there was an error establishing a database connection. How can that be if I triple checked my wp-config.php file and I can post on my blog.

I even reuploaded that file, yet I still get that page showing up when loading various posts/pages on my blog. Plus, if I hit the refresh key after I get that message, my page loads properly….

What is going on?