Job getting failed when am using ntlg Test\SatishG

Hi all,

Am facing an issue :

The job failed.  Unable to determine if the owner (Test\SatishG) of job Backup_Subpaln1  has server access 
  (reason: Could not obtain information about Windows NT group/user 'Test\SatishG', error code 0x6e. [SQLSTATE 42000] (Error 15404)).

_________

Here, Test is my Server Name and SatishG is user.

When am creating a job with windows login  ( Test\SatishG  ) , Sql Server engine automatically makes that particular user as a job owner in sql server agent ( in my case windows login is Test\SatishG ).

When am trying to execute a job ( Backup_Subpaln1 )  it gives me a error as below 

The job failed.  Unable to determine if the owner (Test\SatishG) of jobBackup_Subpaln1  has server access 
  (reason: Could not obtain information about Windows NT group/user 'Test\SatishG', error code 0x6e. [SQLSTATE 42000] (Error 15404)).

So, i have made Owner for a job Backup_Subpaln1  as SA , then it started Executing.

But my doubt is, Even ntlg Test\SatishG is a SysAdmin,But why it shows an error.

And when i started browsing , few blogs talk about Active Directory and am unable to understand it. ( According to my sense when we add  USER(SatishG) inDOMAIN(Test)  then only it allows user to connect through windows login , but why blogs say about Active Directory , Do we have to give any other permissions to user (SatishG) ).

Thanks in Advance..