Check the host firewall on the target system. It could block the connection.
I would also suggest setting up a Profile and using that, if you are using a Domain Service Account to pull the logs. That way you only have to update the password in one place instead of on every Data Source if / when the password changes.
The Service Account needs to have specific privileges on the servers they are going to access.
The firewall on the host system is the first place I would check, after the credentials ("domain\username" and the password).