express 2005: keep on getting sql server does not exist or access denied when trying to backup db

SQL Express 2005 was installed automatically when I installed BES Express 5.x on Windows 2003 R2.  I am following the following pages to try to back up the DB:
http://docs.blackberry.com/en/admin/deliverables/18764/Backing_up_the_BBConfigDB_1154201_11.jsp
I've tried
BlackBerryDBBackup.exe -d BESMgmt -f C:\DB_backup_folder -U sa BlackBerryDBBackup.exe -d BESMgmt -f C:\DB_backup_folder -E BlackBerryDBBackup.exe -d BESMgmt -f C:\DB_backup_folder -U domain\BESAdmin BlackBerryDBBackup.exe -d BESMgmt -f C:\DB_backup_folder -U domain\BESAdmin -P password
but none of them work.
When I go to Database > BESMgmt > Security > Users, I see
dbo, login name: domain\BESAdmin, DB role membership: db_owner
When I go to Security > Logins, I see
builtin\administrators, builtin\users, nt authority\ ...