Cant Create New Sites After WordPress 3.1 Upgrade

What’s your .htaccess?

Did you try turning off your plugins?

My .htaccess:

RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ – [L]

# uploaded files
RewriteRule ^files/(.+) wp-includes/ms-files.php?file=$1 [L]

RewriteCond %{REQUEST_FILENAME} -f [OR]
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^ – [L]
RewriteRule . index.php [L]

Aint tryed turning off my plugins yet.

Let me do that.

Did you pick subdomains or subfolders?

Subdomains

Did you enable wildcard subdomains on the server & in your dns records?

Yes I did.

And spending a whole day playing with it,

Everything good now.