I've been having terrible cookie behavior when I manage my Blogger blog for over a year in all browsers (safari, chrome, firefox). [myname].blogspot.com never recognizes me as logged on.
When I hit "sign in" and get sent to blogger.com, I'm immediately recognized as logged on, but when I return to the public-facing blogspot page, I'm still not recognized (despite reloading).
Finally, I deleted all google, blogger, and blogspot cookies manually (via Safari prefs), restarted browser, and signed in. All worked properly.
I then launched Cookie (which is set for auto removal upon app quit and browser quit), and after the next cycle of launches/quits, the behavior had returned.
I've disabled Cookie and hoping for either instructions or a fix.