After adding a new Json store to a (sizeable) project, I got this error : TypeError: 'undefined' is not a function (evaluating 'b.fireEvent("beforeactivate",b,d)') when I click a model/store. The error seems to come and go, I haven't figured out yet how to reproduce. Restarting doesn't solve, it comes back.
Edit : Some extra detail (sorry, it's just coming back to me), the window in question uses a CardPanel Layout. I added to it a Tool, which seemed to be an issue for architect, the tool is considered as a card somehow and got drawn in weird positions (not on top of the window where it should have been).