I have a multi-domain subdomain network with domain mapping
I added a new admin user and trying to login I get a really odd error, and now anytime I log for any user, including super admin, the same error persists for subsites and the main site.
after a bunch of testing I deactivated Domain Mapping plugin Version 220.127.116.11 and the problem went away, reactivating Domain Mapping brought it back
I tested changing domain mapping settings for administration and login mapping, no luck
subsite.mainsite.com/wp-admin/ or wp-login.php
subsite.com/wp-admin/ or wp-login.php
mainsite.com/wp-admin/ or wp-login.php
from the login page I enter the user and password and it hangs up with a really long URL — but if I open a new tab and browse to the login page the dashboard loads, I guess the cookie is loading but not finishing loading the page upon login
where it gets really strange is in Internet Explorer, hitting the Login button or enter after the password – loads a blank CSS file in Dreamweaver (my default editor) – the CSS file has a very long file name and changes each time
I reinstalled WordPress 3.4.2 from the admin dashboard, updated the network, cleared cookies in IE and Firefox browsers – same results (in browser where cache not cleared access to dashboard without logging in okay), I tested in a subsite with basic twenty-eleven theme, I disabled/enabled single signon in multi-domains plugin
For sure Domain Mapping is the culprit, not sure if it is conflicting with other plugins or something to do with the recent update.