New browser needs needs new firewall?

Internet service has been slowing down for some time up here. Might be roadrunner, might be those distributed denial of service (DDOS) attacks on gov'ment web sites, tired computer, bad karma, who knows.
So I decided to upgrade Firefox to the new version 3.5. Although the new Firefox rendered pages faster it was less effective at getting onto the web. Lots and lots of "cannot find the such-and-such server" error messages, after a lengthy wait for a reply. Try again later and I could get thru. After a few days of this, I took a look at the mozilla website. They had a tab "What to do if you cannot connect with V3.5" That sounded promising. In short, the Mozilla people claim that firewalls are the problem. Turn the firewall off they suggest. Well, not sure about that, especially as the older V3.0.11 Firefox had been working OK for a year on my Zone Alarm freeby firewall.
But, hope springs eternal, I downloaded the latest copy of Zone Alarm and it works. Not 100%, but a lot better. It reduced the "cannot find server" errors to maybe one an hour, whereas with the old Zone Alarm I was getting 10 or 15 such errors per hour.
The V3.5 Firefox is faster than previous version 3.0.11, and with an updated firewall, things are somewhat better than the older software setup.
Lesson learned. Update your firewall more often.