Backup Encryption Key in SQL Server 2008/R2

When trying to backup Encryption Key from ‘Report Services Configuration Manager’ I received below error:

“Microsoft.ReportingServices.WmiProvider.WMIProviderException: An unknown error has occurred in the WMI Provider. Error Code 80070A90”

When verified came to know that the password I am providing for the backup file is not meeting the password complexity policy and hence its throwing error.

So I have tried password having capital letters, small letters and number combination password and it worked perfectly.

Sometimes error will be bit easier to study like if you check the below error I received in another situation it clearly has message stating that issue is with password complexity

Microsoft.ReportingServices.WmiProvider.WMIProviderException: An unknown error has occurred in the WMI Provider. Error Code 80070A90

 ---> System.Runtime.InteropServices.COMException (0x80070A90): Password doesn't meet the complexity policy (Exception from HRESULT: 0x80070A90)
   --- End of inner exception stack trace ---
   at Microsoft.ReportingServices.WmiProvider.RSWmiAdmin.ThrowOnError(ManagementBaseObject mo)
   at Microsoft.ReportingServices.WmiProvider.RSWmiAdmin.BackupEncryptionKey(Byte[]& encryptedBytes, String password)
   at ReportServicesConfigUI.WMIProvider.RSReportServerAdmin.BackupEncryptionKey(Byte[]& encryptedBytes, String password)

Thanks  !!!