I used Radio for a couple months, but decided to switch to Movable Type for a couple reasons (couldn't admin blog from multiple machines, client didn't run on Linux, it was too buggy, templates were a hassle to customize, one blog per install, etc.).
However, I never had a problem with the FTP option. On the FTP option page, I set the username and password to a combination I had successfully used to FTP to my server from a shell login. Other settings I used:
and I checked the box for passive mode FTP.