Problem appending to a file

Hi all.

I have configured a thread to use a FILE protocol so that it will append a billing flat record to a file. Our new pharmacy system does a midnight run every night and generates a billing flat record, which is then supposed to be appended to the filename I specified. However, I notice when I get in in the morning, the file is empty. Now, there are other processes that go on behind the scenes at our site. The billing file is supposed to be processed sometime early morning, and then around 11:00 PM the billing file is archived, and a new 0-length file is created in its place to prepare for the next midnight run. It looks as though all the permissions on the file are OK to me, so I don’t think that’s the problem. Also, when I shut down the thread, turn it back on, then resend the last billing flat record, it appends to the file just fine. Do I maybe have something else set wrong? Would it be better if I didn’t append to the file at all but just overwrote the last one instead, since it has already been archived anyway?

Thanks in advance.

-George