All users' home directories in HCoop setup are located on AFS volumes. The use of AFS implies the use of Kerberos. In essence, your Kerberos (and AFS) "identity" is completely unrelated to your Unix username. While you automatically obtain Kerberos and AFS identity (so-called "tokens") when you log-in to HCoop machines over ssh, be aware that Unix and Kerberos/AFS login are two separate things. That's why the scripts you run unattended cannot write (or read) files because, without extra steps taken, they do not have any useful identity or access privileges to volumes where all the relevant data is residing.
So, in general, when you want to access AFS space (that means any file in your home directory), you first need to authenticate with Kerberos to obtain a valid TGT ("Ticket-granting ticket"). As the name implies, the TG Ticket is then used in automatically obtaining further tickets for access to your files (in AFS) or to specific services (such as to ssh, ftp, bugzilla or members portal).