Losing network browser information

I support a small network in America with 2 Windows 2000 Servers and 2 3COM 48 port switches. The workstations are Win98 and 2000 Pro; I did an upgrade on the servers from NT 4.0 to Windows 2000. We have a corporate WINS and DNS Server in the UK. The problem I have is that I lose my network browser information on all the workstations. To get back the network browser information, I uninstall TCP/IP and reinstall and I will get it back, but then I will lose it again. I am not sure how long it istill I lose the information. What should I do?