Proxy Services Shutting off !!!

My Win NT 4.o Server has M.S. Proxy server. When people come to me and say they can’t get online, I check the M.S. Management Console and the Services ( Socks Proxy, Def. Web Site, Admin. Web Site, Web Proxy, and Winsock Proxy) are all “Stopped”. All I have to do is re-start one of these then it works, BUT randomly they keep shutting off!!! What can I do or check to stop this????