VMM & SCOM Integration is fine, but some Errors on VMM Server found

Hi

I'm getting following error on the VMM Server:

"Credentials are null for user:" from various Eventsources:

Log Name:      Application
Source:        Microsoft.SystemCenter.VirtualMachineManager.2012.Report.VNicUsageCollection
Date:          24.10.2013 08:44:26
Event ID:      25934
Task Category: None
Level:         Error
Keywords:      Classic
User:          N/A
Computer:      XXXX
Description:
Credentials are null for user: 


Log Name:      Application
Source:        Microsoft.SystemCenter.VirtualMachineManager.2012.Report.CloudUsageCollection
Date:          24.10.2013 08:49:27
Event ID:      25934
Task Category: None
Level:         Error
Keywords:      Classic
User:          N/A
Computer:      XXXX
Description:
Credentials are null for user: 

Log Name:      Application
Source:        Microsoft.SystemCenter.VirtualMachineManager.2012.Report.VMHostPowerStateCollections
Date:          24.10.2013 08:49:27
Event ID:      25938
Task Category: None
Level:         Error
Keywords:      Classic
User:          N/A
Computer:      XXXX
Description:
Credentials are null for user: 

Log Name:      Application
Source:        Microsoft.SystemCenter.VirtualMachineManager.2012.Report.VNicUsageCollection
Date:          24.10.2013 08:54:26
Event ID:      25934
Task Category: None
Level:         Error
Keywords:      Classic
User:          N/A
Computer:      XXXX
Description:
Credentials are null for user: 

VMM 2012 SP1 UR3

SCOM 2012 SP1 UR3

MP Version: 3.1.6011.0

Any advice?