Wbadmin "ERROR - No system state backups were found."

I have a brand new 2008R2 SP1 server (Domain Controller) where I try to make SystemState backup. Backup seems to work fine, but I can not delete oldest.
I'm uncertain if I do have a valid SS backup.

I take backup with this command:

C:\>wbadmin start systemstatebackup -backuptarget:D:
wbadmin 1.0 - Backup command-line tool
(C) Copyright 2004 Microsoft Corp.

Starting to back up the system state [04-08-2011 08:45]...
Retrieving volume information...
This will back up the system state from volume(s) Local Disk(EFI System Partitio
n) (200.00 MB),C-OS(C:) to D:.
Do you want to start the backup operation?
[Y] Yes [N] No y

Creating a shadow copy of the volumes specified for backup...
Creating a shadow copy of the volumes specified for backup...
Windows Server Backup is updating the backup for deleted items.
This might take a few minutes.
Found (96) files.
Found (13207) files.
Found (29482) files.
Found (39566) files.
Found (78588) files.
Found (79088) files.
The search for system state files is complete.
Starting to back up files...
The backup of files reported by 'Task Scheduler Writer' is complete.
The backup of files reported by 'VSS Metadata Store Writer' is complete.
The backup of files reported by 'Performance Counters Writer' is complete.
Overall progress: 1%.
Currently backing up files reported by 'System Writer'...
 - continuing to 100% -

Summary of the backup operation:
------------------

The backup of the system state successfully completed [04-08-2011 08:59].
Log of files successfully backed up:

--------------------------------------------------------------------------------------------

If I check the backup with "Get Versions", I get this:

--------------------------------------------------------------------------------------------

C:\>wbadmin get versions
wbadmin 1.0 - Backup command-line tool
(C) Copyright 2004 Microsoft Corp.

Backup time: 30-07-2011 21:00
Backup target: Fixed Disk labeled D:
Version identifier: 07/30/2011-19:00
Can recover: Volume(s), File(s), Application(s), System State
Snapshot ID: {6f4f38c8-3d3c-4e9f-87fb-d7cdb9c13c59}
 - several other backups-

Backup time: 04-08-2011 08:45
Backup target: Fixed Disk labeled D:
Version identifier: 08/04/2011-06:45
Can recover: Volume(s), File(s), Application(s), System State
Snapshot ID: {ae749899-447f-4c6d-b2d3-06c2f1816541}

--------------------------------------------------------------------------------------------

So far everything seems ok.
But when I try to delete the oldest backup, things look weired:

--------------------------------------------------------------------------------------------

C:\wbadmin delete systemstatebackup -deleteOldest
wbadmin 1.0 - Backup command-line tool
(C) Copyright 2004 Microsoft Corp.

Enumerating system state backups...
ERROR - No system state backups were found.
This command can be used to delete backups that only contain the system state.

--------------------------------------------------------------------------------------------

If I try with -keepversions, I get same result:

--------------------------------------------------------------------------------------------

C:\>wbadmin delete systemstatebackup -keepversions:1
wbadmin 1.0 - Backup command-line tool
(C) Copyright 2004 Microsoft Corp.

Enumerating system state backups...
ERROR - No system state backups were found.
This command can be used to delete backups that only contain the system state.

-------------------------------------------------------------------------------------------- 

So do I have a valid Systemstate backup ?
And can I trust I can use it to recover if needed, since it says "No system state backups were found" ?
And why can't I delete the oldest backup ?

- Duelund