Scott Lovegrove has solved this problem for everybody by creating the Windows Live Writer Backup Utility, which can even be run with command line arguments for automating backups.
The interface of the application is simple enough, all you really need to do is click the world’s biggest Backup button and specify the location to save the file.
You can also start it from the command line with any one of the command line arguments.
Note: If you are running this in Windows Vista you will need to choose to run it as administrator.
Download Live Writer Backup Utility from ScottIsAFool’s Dev Stuff