SQL job cannot access Microsoft Excel DCOM application. Permissions are set. What gives?

I have a SQL job that runs a VB script that uses an object provided by the Microsoft Excel DCOM application. Excel 2003 is installed and working. Both SQL Server and SQL agent run under mydomain\thataccount.

The error is:

The machine-default permission settings do not grant Local Activation permission for the COM Server application with CLSID {00024500-0000-0000-C000-000000000046} to the user mydomain\thataccount SID from address LocalHost (Using LRPC). This security permission can be modified using the Component Services administrative tool.

The following findings make this difficult.

1. mydomain\thataccount has full Launch and Activation Permissions, Access Permissions, and Configuration Permissions on the DCOM application in Component Services DOC Config.

2. The error (above) claims that it doesn't.

3. If I grant "everyone" full access of all types, the error doesn't change.

4. If I make the SQL agent run under another account (mydomain\otheraccount), the error still complains about mydomain\thataccount not having permissions. Apparently the job runs under SQL Server credentials rather than SQL Agent credentials.

5. I did not change the account SQL Server runs under because when starting SQL Configuration Manager I got this error (which might or might not be related):

   Cannot connect to WMI provider. You do not have permission or the server is unreachable. Note that you can only manage SQL Server 2005 and later servers with SQL Server Configuration Manager. Invalid class [0x80041010]

6. If I add mydomain\thataccount to the local Administrators group and restart SQL Server, the job works. This means that an administrator has permission to use the DCOM application but a non-admin user does not, despite being given permissions.

7. To reiterate: even when "everyone" was given full access to the DCOM application, the error said that mydomain\thataccount doesn't have permissions to access the DCOM application.

Any ideas?

(I am starting to believe that something is wrong with the Windows/SQL installation.)

Microsoft® Windows Server® 2008 Enterprise Version: 6.0.6002 Architecture: 64-bit Status: OK Total Visible Physical Memory: 3,927 MB Windows Service Pack: Service Pack 2

Microsoft SQL Server 2008 (SP1) - 10.0.2531.0 (X64) Mar 29 2009 10:11:52 Copyright (c) 1988-2008 Microsoft Corporation Enterprise Edition (64-bit) on Windows NT 6.0 (Build 6002: Service Pack 2)