ESXi 5.1 doesn't show the Active Directory groups to add permissions

Hi,

I joined my ESXi 5.1 to my new domain(2012 domain).

I went to the permission tab to add users for them to authenticate to the ESX with the Vsphere Client.

It all went well when I add users, however I still have some issues:

1. Not all users are shown under the "Users and Groups"

2. When change to "Show Groups First" I  cannot see any group which I've manually created in the Active Directory. All I can see is the built-in groups of the AD.

When I try to search for a name of a group it says that this group does not exist

3. I created the ESX Admin Group in the AD, But I cannot see it on the ESX.

In the pic you can see that it shows only the built-in groups from the AD.

Please help.

Thank you.