I've just published 0.20.2 - rather sooner than planned.
This fixes a bug in the editor that, under a very particular set of circumstances, can cause it to load multiple copies of your flows at the same time. This in turn causes all of the wires to disappear and it to generally behave oddly.
I'm surprised it wasn't hit during the beta as it has been lurking in there from the beginning of the 0.20 stream. But there we go.