Windows Server 2003 running DNS, network 75 users or so, XP and WIN7 replaced router and browsing now locks up using IE, Firefox, and Chrome. Replaced router again and verified it's not the point of failure (could be convinced if good enough case made).
Problem is intermittent enough that browsing works on some computers for awhile then freezes hourglass while waiting for content to upload.
Did the usual ipconfig /flushdns, renew /release, ran intodns.com, dcdiag /test:dns, put old router back in works fine. Problem is the old router is 100M new one is 1G needed for new network from new ISP.
When browsers lock up clicking stop then refresh site pops up immediately.
DHCP running on the server (off on firewall), firewall has the latest firmware and has been replaced.