Scenerio: No users were able to authenticate to the SEPM Console (v: 11.0.6200.754) remotely. The error given was "Authentication Failure. Please try again". I was able to log in locally to the console on the server, and checked all accounts to make sure they weren't locked. None of the accounts were locked.
Resolution: The problem was discovered in Admin>Servers>ServerName>Directory Servers tab. We only had one domain controller listed and it was recently decommisioned, hence our problem. Added all the active DCs. I also had to go through each individual admin account and point them to a DC that was in service. I scattered the accounts out so we all don't get locked out the next time this happens.
Hopefully SEPM 12 will allow us to just authenticate to the domain instead of specific controllers.