Hopefully nobody will attach a 20MB file here, that would seem excessive.
Obviously, something on your side is preventing ftp access and it should be easy to fix. Are you behind a cheap firewall that does not use an ftp-alg. Is there a corporate policy that prevents downloading of executables? Are you behind a router? Do you run any kind of personal firewall software? What are your browser security settings? Have you tried active (PORT mode) ftp and passive mode ftp or even a different browser (e.g. firefox: http://www.mozilla.org/products/firefox/ )? Have you tried a dedicated ftp client or even commandline ftp? Maybe your antivirus program is the problem.
Do you have ftp problems only with the NI site, or in general.
What is your O
S?