SQL Server agent job failing to back up database

I have set up a SQL server agent job to back up database on regular basis.. For some reason the back up fails.. Could not find any meaningful info in the logs.. Transaction logs are getting created for the same DB but not the database back up..

The below is my environment..

MS SQL Server 2005 - 9.00.1399.06

Windows 2003 server SP2

Any pointers would be helpful.. I checked the event logs and the agent logs and did not see obvious error.

Thanks