Yeah, it seems the sheet was just protected. Why?

It's a consequence of the high number of requests for the doc. It started working for me after a short wait.

Edit: hmm... or maybe when this happens it's because the owner is temporarily taking the the document offline to fix it when people mess it up?

Interesting. I wonder why Google throttles it like that.

Because editing google doc spreadsheets isn't sharded.

Same here.