Using the geo-coding functions, Cloudmade free server works fine. Since I prefer using 2 different sources and comparing the results, I set up a different field for the Yahoo results.
Using the Yahoo free server I get the following warning: "Forbidden (HTTP error 403): The page you are trying to access is forbidden."
Yahoo are blocking our / your use of geocoding either due to rate limiting or breach of terms of free service. We are looking at alternative options.
Meanwhile you should use cloudmade, or consider using a lookup file - for example, the full UK postcode database, and other data files, are now freely available from geonames:
Hi Steve, thanks for your rapid respons. I googled the problem as well, and I found an announcement that Yahoo changed the required API in September. Could this be the reason that they are blocking us?