Network problem in Win 2003 Standard Edition

I have an IBM X Series 226 server installed windows 2003 server, earlier this system is accessable to all the systems and the files which were shared is also seen by the clients (other systems), but now it is not accessable for others, but this system is showing all the client (other systems in its network)
Pls help me to solve this problem. I am tried by uninstalling network card and installing it again, but it does not serve the purpose