OK, looks like about 12 hours of downtime either way. We think we don't have to roll back but the fix is a code change and that takes several hours to implement, build, test, and deploy. I'm hoping for less but that's my current best guess. We will be posting updates as we have more news. But go to bed or get on w/ your day or whatever.
Sorry, folks.
Edit: To clarify my earlier tiny (2-hr) predictions - I kept hearing things that made me think we could either live w/ this or fix it w/o code. I should know better than to get my hopes up like that. Particularly should know better than to get your hopes up like that.