We have seen quite a few cases come in, so I figured I would post publicly.
With the SEDR 4.3 update, we introduced the ability to add multiple AD Domains for AD login to the web interface of SEDR. Since this update, the NetBIOS field is now required so we can determine which AD server to query for the login. If you have the NetBIOS name set before the update, there will be no problem. The issue is that many customers did not provide this field since it is not mandatory.
More information and a screen shot can be found here: