As first step I'd check the instructions detailed in the link i've posted earlier on.
Also, I'm not 100% sure, but I would look at security issues between the two linked servers: how did you configure the security mappings between the two servers? Also, I don't think that NT AUTHORITY\SYSTEM is a valid account on linked servers as it depends on the machine it's running on (that is, it is on both servers, but it's a "different" account on the two servers - I might be wrong here tho).
Try creating a new Active Directory account with limited privileges, grant it the access level you need on both servers and use that account for the login mapping: hopefully that should sort your issue.
As I said, I'm not 100% sure, but that's the path I would follow to sort this issue
Hope this helps, post again otherwise