If you're having any problems downloading something from there, it could be one of three things as a rule.
1) It only allows so many simultaneous connections, to keep it usable for people who are downloading. The bandwidth itself is limited, so it's just to stop things running like a dog on downloads for everyone.
2) You're behind a firewall that's arsing up ftp.
3) You're using IE.
Only the small files are actually on the http site. The large files are stored on the ftp server, and linked to from there. Some firewalls, and IE as a rule, tend to cock up ftp access. If neither of those are the problem, just try again later on.