I received this msg when trying to log into TB with Firefox :
Please enable referers in your firewall or browser and try again
I didn't have to change any thing in my hosts file to remedy the prob.
changing the value of Network.http.sendRefererHeader in firefox from 0 to 1, or the default of 2 fixed the problem for me.
You can change the value of this setting by typing about:config in firefox url bar or add this line to user.js
hope it helps
user_pref("network.http.sendRefererHeader", 1); // default 2