Can't check out - finally worked on chrome as guest

I've tried a thousand things to get a fairly large order through. Got the error message during checkout using IE, Firefox, and whatever browser is on friends phone. Tried in-private browsing session as suggested, deleting cookies and tracking, etc. Finally worked after downloading Chrome, logging in to get cart, deleting all cookies, AND then checking out as a guest. Shew. Maybe that will work for someone else too.