In looking at your mailserverclient_error-0.txt I see the following:
Microsoft Exchange Load Generator
Configuring LoadGen task engine...
Loading settings...
ERROR -- Caught exception UnauthorizedAccessException:
Access to the registry key 'Global' is denied.
at Microsoft.Exchange.Swordfish.TaskEngine.initializeUserGroups()
at Microsoft.Exchange.Swordfish.TaskEngine..ctor(GlobalSettings settingsObject)
at Microsoft.Exchange.Swordfish.Cmd.SwordfishCmd.Main(String[] args)
Are you sure your client0 is a member of the Mailserver0's domain, logged in and is using the correct credentials?