I think I've found the solution! Follow these steps:
1. Disconnect from the Internet: either turn off your WiFi connection to your router, or unplug your Ethernet cable. (You can also unplug the router itself, or disable the internet connection in other ways)
2. Open TT and get the "update" message, but now it says "To get software updates, you need to connect to the Internet".
3. Click on "Cancel"; TT comes up without downloading and installing the updates. You can open a previously started return, for example.
4. Re-connect your computer to the internet.
4. I've found that, next time you want to start TT after a shutdown, it'll come up without asking to do updates; it seems to now remember that you don't have access (even though you do).
6. At some point (say, prior to doing a final check), you might want to "force" an update (either download the 250MB update file, or do it from within TT -- Online / Check for Updates).
I hope this works for everyone!
