Plugin install isn't working–WPMU dashboard

I’m attempting to install Marketpress from the WPMU DEV Dashboard. I have not set up one click installation (and I don’t want to do that at this time), but when I click on “Manual Install” nothing happens. What am I doing wrong?

On another note, is it really safe to set up one-click installation by adding the ftp creds into the wp-config file? Is it even safe to enter the ftp creds into the wp dashboard at all? I’ve always wondered about that–isn’t that just a major security risk? If not, why not?