Here we go:

Error: attempt to concatenate field `formatUnits' (a nil value)
AddOn: Questie
File: QuestieTracker.lua
Line: 299
Count: 1

We do not support Questie 1.0 anymore. Please update to 2.0.

When was it released and wherw is it?

Found it.

When you switch, you might have to clear your WTF folder of all "Questie.lua" and "Quesite.lua.bak" files (before you start WoW). Otherwise it MIGHT cause issues (it didn't for our testers, but some people complained).

As usual. :)