How to reproduce:

1. Hop into a dungeon
2. Start combat
3. Open map
4. Click the circular icon of a boss to open boss loot table
5. See error in chat "Interface failed because of an addon" and no loot table interface

I've had a couple of bugs like this before and have been testing the addons one by one, there are a couple of other addons that produce this bug as well.

There is no LUA error but the interface fails. Other addons that have the same behaviour are: Handy Notes, TomTom and World Quest Lists

I hope you have better luck finding out what is the problem as I have not been able to get LUA errors out of this.

If it's that widespread, it's probably either something in Ace (unlikely), or something where Blizzard has made a common addon function tainting again. They occasionally accidentally make things like "showing a tooltip" destroy everything...

It does seem to be something of the sort. I was surprised that I didn't get any LUA errors, even tried using buggrabber with bugsack to see if it caught anything but nothing popped up