About a week ago most of the computers in our work group started to exibit a problem. While using IE or Firefox the browser just looses its access to the internet. The user gets the page not found error. I can ping the downed computer from another and I can ping from the computer and download but IE and Firefox won't connect to the internet. The only way to restore operation is to reboot. I've run ad-aware, spybot and online and offline antivirus such as activescan and trendmicro with no help. I've turned off DNSCache and det MaxCacheTtland MaxNegativeCacheTtl to 0 in the registry. We are running 2000ProSP4, Zone Alarm and AVGPro. A few of the computers run Norton Firewall.
Any help will be greatly appriciated.