Integration Services :: SSIS Cannot Open Datafile When Executed From Remote Host

I have seen several problems posted where an SSIS package writes a file successfully when executed manually, but fails when executed via SQL Agent job..I have the opposite problem. I'll try to lay it out succinctly: SSIS writes to a file on a shared folder, specified as HostAShare, for example. I created the share and gave full control to Everyone (out of frustration).I'm working from HostA via RDP, connected to the DB on DBHost via SSMS.If I kick off a SQL Agent job that executes the package, it works fine. (SQL job is running under SQL Server Agent Service Account).If I execute the job interactively (logged in to SSMS with Windows Auth), it fails with "Error: Cannot open the datafile "HostASharefilename.ext""We did find that if I RDP directly to the DBHost, I am able to execute manually.Also, if I try executing an xp_command shell command to write a file to the share, it works. (When RDP's into HostA with an SSMS connection to DBHost under my windows domain auth, as above.)The problem is the same when I RDP to any remote host.