map drive problem

dear viewers ,i have one problem, in our office Win 2003 server and xp professional in client side, some time from client side map drive did problen when the rest of time i want to open map drive it was not responsed and given contect error and then i restart the system it did well.but during this time it was ping to server very well continously.but connection earch???
i will be appriciate to you for give me solution. thnks and regards.