I'm having problems with several Windows 7 Pro machines which I have just added to a Windows 2003 server network. After a while the machines seem to lose connection to their network shares and printers. I am able to ping the server but unable to browse to it or any shares using the UNC path. Browsing by IP address allows me to view the share. Incidently a reboot fixes the problem but it returns again a little while later. All the other client PC's (XP) machines are fine, its just the Windows 7 PC's which are experiencing this issue. Any ideas?