I have developed a project which uses an external dll as FTPServer, I have created the FTP Server on my project like this:
private ClsFTPServer _ClsFTPServer;
You've probably already tried this, but just in case, have you tried wrapping it in a try catch?
try catch
try { _ClsFTPServer = new ClsFTPServer(FTPUserName, FTPPassword, FTPPath); ... } catch(Exception e) { ... }