Smart FTP Cannot Log In

I have been using Smart FTP for about 1 year and have never had a problem until today.

There is a particular FTP account that I cannot log into. Other accounts on the same work properly. I ahve checked the user name and pass and they are fine. In fact I can log into the account with my browser (IE7) but not with SmartFTP.

I have checked all settings and have compared my set-up for this ftp account with my other working FTP accounts and cannot see anything different.

Any advice or suggestions?