What kind of FTP did you say you used?
I'd just like to make a small note about protocol acronyms, and the importance of knowing the correct acronym when naming your BizTalk adapter so that someone planning to (re)use your adapter knows what it's really about. The case I'd like to highlight refers to FTP, and is something I've been forced to drill myself into when working in an environment where several different types of similar sounding acronyms are present.
FTP, the File Transfer Protocol, is used to transfer data from one system to another. The base implementation of this protocol sends all data (including username and password) in clear text through the wire. There are however protocol enhancements for securing this transfer using SSL. This is called FTP over SSL, which is more generally refered to as FTPS (or FTP/SSL). There is also the option of securing your FTP transfer by tunneling it though a SSH session. Though since FTP is a multi channel protocol this in many implementations just protects the control channel (ie the username and password) and sends the data unprotected. However this differs from implementation to implementation, and in some cases both control codes and data is protected. This is refered to as Secure FTP, but is not to be confused with SFTP, which is used when talking about the SSH File Transfer Protocol, which has really nothing to do with FTP. Confusing isn't it? ;)
Wikipedia har more info. FTP (and FTP over SSH), FTPS, SFTP.