vCenter issue - A general system error occurred: Cannot get user info

Hello,

I have  one VMware vCenter Server 5.1.0 (not an appliance) to manage ESXI 5.1 Hosts. I have a probelm related to Active Directory Authentication with vSphere Client to the vCenter Server.

My problème is when logging in to vSphere Client to vCenter Server and using Active Directory Authentication account credantial , I am getting an error stating "A general system error occurred: Cannot get user info", but when i check a checkbox "use Windows session credentials" that work without problem.

   So i found alot of solution without fixed issue :

            - I have checked DNS, and can perform a forward and reverse DNS lookup with nslookup..

            - have also gone into the Web GUI and set the vCenter Single Sign On Identity Source as indicated in the following web links, and added several domain groups as authenticated users to the vCenter Server

                    http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=2035510

I was working fine last week, and then today I lost the ability to login again with AD credentials. Can someone please direct me to fixing this annoying problem?