Cannot open backup device 'F:\foldername'. Operating system error 5(Access is denied.).

SQL 2005 Enterprise

Even if I logon as Administrator and try to backup any of my databases to local partitions, I get this error below. I have been operating fine up until this point and doing backups all the time.  As far as I know, and after checking, no permissions have changed and of course Administrator has ntfs permissions to my local C and other partitions on this server:

TITLE: Microsoft SQL Server Management Studio
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Backup failed for Server 'servername'.  (Microsoft.SqlServer.Smo)

For help, click: http://go.microsoft.com/fwlink?ProdName=Microsoft+SQL+Server&ProdVer=9.00.1399.00&EvtSrc=Microsoft.SqlServer.Management.Smo.ExceptionTemplates.FailedOperationExceptionText&EvtID=Backup+Server&LinkId=20476

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ADDITIONAL INFORMATION:

System.Data.SqlClient.SqlError: Cannot open backup device 'F:\foldername'. Operating system error 5(Access is denied.). (Microsoft.SqlServer.Smo)

For help, click: http://go.microsoft.com/fwlink?ProdName=Microsoft+SQL+Server&ProdVer=9.00.1399.00&LinkId=20476

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BUTTONS:

OK
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In the Event log for Windows Server 2003 I see this:

Event Type: Error
Event Source: DCOM
Event Category: None
Event ID: 10016
Date:  3/6/2006
Time:  3:35:06 PM
User:  NT AUTHORITY\NETWORK SERVICE
Computer: servername
Description:
The application-specific permission settings do not grant Local Activation permission for the COM Server application with CLSID
{BA126AD1-2166-11D1-B1D0-00805FC1270E}
 to the user NT AUTHORITY\NETWORK SERVICE SID (S-1-5-20).  This security permission can be modified using the Component Services administrative tool.

For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp.