MS SQL Server 2000... Error Backing Up Database

Hi

I am getting an error while backing up a particular database named "asset" . The error says ........

Server: Msg 3132, Level 16, State 1, Line 4
The media set for database 'Asset' has 2 family members but only 1 are provided. All members must be provided.
Server: Msg 3013, Level 16, State 1, Line 4
BACKUP DATABASE is terminating abnormally.

I have created two backup devices for this database ("asset") through enterprise manager.
AssetDMP
AssetLogDMP

I have total 9 databases out of which only this database throws error. All other database backups going fine.

Here is the query that I am using to backup the database and Log.

USE master
GO
IF EXISTS (SELECT * FROM sysdatabases WHERE name = 'Asset')
BACKUP DATABASE Asset TO AssetDMP WITH NOUNLOAD, STATS=10, INIT, SKIP
GO
IF EXISTS (SELECT * FROM sysdatabases WHERE name = 'Asset')
BACKUP LOG Asset TO AssetLogDMP WITH NOUNLOAD, STATS=10, INIT, SKIP



Please Help

Thank You / Ssg