How can I stop Firefox throwing a NS_ERROR_FILE_CORRUPTED error?

Firefox stores its HTML5 data in a file called webappsstore.sqlite. That's sitting in your profile directory which lurks somewhere in ~/.mozilla/firefox/....default/ (depending on what your profile is called).

Move that out the way and restart Firefox and everything will come back to life.

• More: https://developer.mozilla.org/en/dom/storage

What fixed it for me when I had that error with BitBucket (again) was the clicking the button Clear Cookies and Site Data.... You can arrive at that button by clicking at the symbols right before the web address (an i withing a circle, or a green lock, or a crossed out lock, or something similar). Then you get a popup dialog at the end of which you can find the aforementioned button:

I was able to resolve this issue using a procedure similar to the one outlined in https://superuser.com/a/1329161 (replace places.sqlite with webappsstore.sqlite in those instructions). The advantage is that this preserves (uncorrupted) content of webappsstore.sqlite, which contains local storage data.