Here is a work around that worked for me:
In wp-config.php, make sure the line:
define( ‘COOKIE_DOMAIN’, ”);
exists and IS NOT commented out.
If you already had a sunrise.php file in wp-content replaced it with a copy of the one thats in wordpress-mu-domain-mapping. ( you can just move the original to the desktop or someplace you can get to it if you want to put it back later… and make sure the sunrise.php file your copying is still also in the wordpress-mu-domain-mapping directory )
Then edited the sunrise.php file commenting out line 5-7 which should now look like:
/*if ( defined( ‘COOKIE_DOMAIN’ ) ) {
die( ‘The constant “COOKIE_DOMAIN” is defined (probably in wp-config.php). Please remove or comment out that define() line.’ );
}*/
**Make sure to remember to save after making changes**
Now you should be able to log in, and domain mapping should still be working.
