Every time I open a new game, to start editing, it gives me a report saying that my XML is invalid and I cannot load or edit my game. I am using Google Chrome's latest update, and I am on a Lenovo Chromebook.

What kind of game?
If you're using Quest with the online editor, then your XML will come from your selections on the first screen. Text adventure/gamebook, and the language you've selected. It's possible that one of the language packs has been corrupted, maybe. Which mode and language are you selecting?

(If it's not Quest, I can't offer any advice)