addlocale will clean your rpm-cache before downloading the needed packages. This is needed to get this fancy progress dialog window working
4.0-6 works fine here using PASS, KDE, and British English.
Try running it again, maybe there was some network timeout.
Or you can try to edit as root /usr/bin/addlocale and at line
a) 1852 change sleep 1
to sleep 2
b) 1862 enter sleep 5
, then save the file and run addlocale with this and let me know if this helped.
I will only have time tomorrow to look into this any further.