Update: 9th November 2013 - the all new Kindle Paperwhite has been released for international shipment - check out this post for more:
However if you are just trying to fix you Kindle 3 - read on:
So after 5 days of having my new Kindle 3 3G/WiFi e-reader I started to wonder why it would never connect to a 3G network when I wasn’t connected to a WiFi network. It would connect EDGE even when in a clearly de-marked 3G coverage area and even when my iPhone showed that there was a 3G network available.
Dread suddenly filled me as I thought that maybe my Kindle, which after only 5 days already I had become inseparable from, could be faulty and after reading the warranty I realised that this could mean sending it back to Amazon for them to assess this before sending me another. That was not an option and with my technical head screwed on I got to work on Goggle looking for an answer.