I have 3 Win XP machines connected to a router, which I connect to one of three ISP's (I'm overseas, so sometimes an ISP is not working very well). All 3 machines are set up with the LAN to use DHCP to set the IP and to automatically get a DNS server. All are using ZoneAlarm Security Suite. This works fine always on 2 machines, and usually on one of the others -- i.e. I can switch ISP's, do the "Repair" on the connection, and then continue working.
However at times this one machine (and this one only) will be unable to resolve names tho it has internet connection -- I can't get to any website via DNS. Sometimes if I disable the LAN and shut down browsers/Skype/... the problem will get resolved when I enable the LAN again. But oftentimes, that doesn't work. The only thing left that fixes it is rebooting, which is something I'd rather avoid.
So I'd like to know a way around rebooting when this does happen, or at least to understand the cause of the problem and perhaps some ways to avoid it.