I use firefox on 3 client: 2 windows ( 10 x64 and 7 x74) and one linux (debian testing). With the windows edition i see slow connection on https, on linux is ok. I've tried also firefox beta on one windows installation, without effort. Actually i'm using V 43 on win, and V 44 on linux and win 7. All of this firefox profile are connected through firefox sync. A Ccleaner clean doesnt help, even new firefox profile doesnt help. This slow connection means that firefox are looking for page for some seconds and then fail, asking me to report error (that i've reported). This happen pretty always with pfSense https webpages and other config page, some weeks ago all were fine; also open this site on other browser is fine. Sorry for my english, i hope i can help you. regaards