Steve,
I'm sorry you are having this trouble. I just deleted CA & NV from my android tablet and re-downloaded all that data. It was smooth and fast, no errors. So I'm fairly confident it's not a server or a data issue causing the problem. I'm also using version 8.1.70.
Can you send a bug report? Perhaps the log file will shed some light. Also when you get the download errors if you could switch to a web browser and try browsing the internet, that might help. Specifically try and navigate to www.iflygps.com (which is also our data server) - this would eliminate basic connection issue to our server.
If these test okay, you might consider deleting / reinstalling iFly GPS. Or you could try moving the data to an SD card, if you have one you can install.
Thanks,
Walter