I have problems with two Windows 7 x64 machines - every few days they lose internet/network connection, though my Windows XP x32 and Linux x64 machines do not have any such problems. Since I had problems with ZoneAlarm on the Windows 7 machines initially (screen kept freezing every day or so), until I updated to, I wonder whether ZoneAlarm may be causing this issue (note all the Win XP and Win 7 machines are using ZA Internet Security

Notes: The router is a Billion 7800N. The network is CAT6 wired throughout (no wireless use). The 7800N is linked to a Netgear GS724T smart switch along with all the PCs and other devices on the network.

When the issue occurs, the Windows 7 machine cannot see the internet via IE8, local VNC does not work, yet I can ping other machines on the network and various websites(?). If I let Windows 7 try to troubleshoot the problem, I get the following message; "Your computer appears to be configured correctly ......".

If I disable the network adapter and re-enable, the problem is not rectified.
The only way I have been able to get round the problem so far is to reboot the PCs this is not acceptable as the machines are all required for 24/7 use.

Any help gratefully recieved.