I am having an issue on the Mac OS X after updating to 6.12 where the GUI expands the window wider than my screen resolution and will not allow me to shrink the window to fit on the screen - very weird. I opened a ticket and kovid has looked but it is not reproducible as far as he can see. I tried deleting the dynamic.pickle file, but that didn't work. I was wondering if anyone else has had this happen. I have attached a screenshot to the ticket:
http://calibre.kovidgoyal.net/ticket/3484