Binos,
I was getting a login pop-up window for "mygulfair" a few days, which seemed to sort itself out after I posted about it on Pprune. No-one else seemed to have the problem.
Do you have "Block Pop-up Windows" selected on the Mac: Apple-K ? Don't put an antivirus program on your Mac, whatever you do. It's probably just an annoying, but persistent bit of Javascript.
Applemacster