I started to ask a question on UX.stackexchange.com and I clicked to add a UI Wireframe and it doesn't seem to allow me to save.
After setting up my wireframe which worked fine, I clicked "Save and Close" and all i see if an empty white popup that never seems to go away (see screenshot below). I have included a screenshot below.
I get the same behavior using Chrome v37 or Firefox v32 on Mac.