The recent changes have GeoRSS tags in the "GeoRSS simple" format. The "ACME GeoRSS Viewer" only supports tags in the deprecated "W3C Geo" format. See http://www.georss.org/ for details.
I could add a parameter to the feed to overwrite the default output format, if you are interested in it.
Edit :
I fixed a bug with the rssToGeoRSS converter. You can now use it to convert the Geonames recent changes feed into a feed using the W3C format.