Just updated from 1.50a2 to 1.50a4 and can no longer open any craft window on any toon.

renamed Skillet-Classic.lua in account saved variables with no change. Back versioned to 1.50a3 and it opens again. Downloaded from Curse app.

Two choices... Install Skillet-Classic-1.50-alpha5 or install the addon Altoholic (I forgot to test the case where the Altoholic addon wasn't installed).

I'm also having the same issue.