Unable to resolve host name


I have a company that I get there inventory from via FTP. If I go to internet explorer and type the appropriate FTP site (ex- [url="ftp://23.456.78.901)"]ftp://23.456.78.901)[/url] enter user and password the ftp site will open just fine when I go to 'page' and 'open in windows explorer'. However, when I want to open the site in SmartFTP...I type in the destination field and enter the correct user and password, I am unable to connect and SmartFTP says 'unable to resolve host name'.

My thinking is this is something the distributor is not doing n their end to allow me to access the site via Smart FTP. I would really appreciate some suggestions I can tell them or perhaps what I am doing wrong. I know the site, user and password are all correct because it opens in internet explorer.

Thanks a million and any help is greatly appreciated.