Whenever we install a mod on my forum some of the files do install but not all and they say we need to put in the FTP info,we do and nothing happens. Also it always says this Some of the files this package needs to modify are not writable. This needs to be changed by logging into FTP and chmoding the files.
Maybe you can't chmod files that need to be chmoded for mod's installation. I know some hosts disable this on their servers.