When using Firefox 1.5 with ZoneAlarm (Internet Security Suite, Version 6.1), I found I had to set ZoneAlarm Cookie Control (in Privacy, Main tab) to Off , NOT Medium . Otherwise some legitimate cookies were not accepted, even if Allow sites to set Cookies (in Tools, Options, Privacy, Cookies tab) is checked in Firefox.
(This puts your Firefox settings in control of cookies.)
Otherwise, NY Times website and others that worked well with Internet Explorer 6 SP2 did not. My clue to fixing the problem was that some sites reported that the Firefox browser was not accepting cookies. For reference see http://kb.mozillazine.org/Websites_r..._they%27re_not .

P.S. Forum Website Managers: Time to allow ZA ISS Software-Version selection of 6.1 .

Operating System:Windows XP Pro
Product Name:ZoneAlarm Internet Security Suite
Software Version:6.0