Originally Posted by HarryT
The symptoms you describe are nothing to do with Amazon locking anything down; it indicates a problem with your local 3G coverage. Try taking your Kindle a couple of miles away and try to connect again. I suspect the local cell tower has a fault.
The funny thing is that the 3G indicator is on when this happens, with a strength of 4 or 5 bars... that's why I thought it might not be purely a connectivity issue.
Thanks for the suggestion, I'll give it a try!