I've been working in Create a World/ Edit in Game Mode for well over a year, and this is the first time I keep coming across this issue.

All of a sudden, the GUI while I'm editing a Lot in Build Mode just breaks (clicking on live mode/buildmode/etc does nothing), and when I click anywhere, I get odd commands like "Thumbnail camera" and "toggle charred state." I'm apparently in some kind of special mode, but because I had no idea how I got into it, I don't know how to get out of it. It just happens spontaneously. When this happens, I can't save anything. What can I do? I just spent an hour editing this lot.; now I can't save it.

Edited to add: Just figured out how to break out of this, but I'm leaving this up in case someone runs into this frustrating problem. If you find that the buttons suddenly go "dead" (clicking on them doesn't do anything) and you get buttons like "Lock", "Thumbnail camera", etc., press F5 so you can bring up the options menu, then go to Edit Town and save from there.