I'm not a replication expert but it seems that the Distribution Agent cannot connect to SQL_C using the A_user login.

-Mike

>I am trying to replicate a database to server SQL_C, but get an error
>"The process could not connect to Subscriber 'SQL_C'.Login failed for user A_user"
>
>Other database on the same server are replicating to another server SQL_B with no problems, I have tried this database and this work OK to SQL_B
>
>All servers have the same users and the same SQL_agent
>
>What is the problem?