First, sorry for my english.
If i try to upgrade my arch box, pacman say to me that all remote database are unreacheble.
So i tried to modify the XferCommand like this :

XferCommand = echo %u

and i discover that the url isn't correct :

ftp://ftp.archlinux.org/testing/os/i686/testing.db.tar.gz/testing.db.tar.gz
ftp://ftp.archlinux.org/current/os/i686/current.db.tar.gz/current.db.tar.gz

the correct one is ftp://ftp.archlinux.org/testing/os/i686/testing.db.tar.gz/

i resolved the problem with this XferCommand :

XferCommand = echo %u | awk '{ print(substr($1,0,index($1,"gz/")+1)) }' | xargs /usr/bin/wget --passive-ftp -c -O %o


bye :)