RE: A general system error occurred: Cannot get user info

Just ran into the same issue.  Corrected it by logging into the appliance web management console (https://[vceneterIP]:5480 in my case), logged in with local account (root) and re-entered domain and credentials on vCenter Server>Authentication screen.  Rebooted just to be sure and working fine now.  I've also created a new account specific for vCenter to use, so I took the oppotunity to change from a frequently used login domain admin account to the new account, both worked after re-applying the AD settings.  All of this was after it broke after applying the build update to 5.1.0.10000 Build 1065184.

For what it's worth...