Blocked access to batch file
If you are running the batch file through xp_cmdshell you are using a different set of permissions.  Here is the BOL entry for xp_cmdshell.

Basically though if you are running it as a sysadmin then xp_cmdshell uses the service account for SQL Server, not the service account for the Agent.  If you are not running it as a sysadmin then it uses a proxy account.  The proxy account is stored in credential called ##xp_cmdshell_proxy_account##.