client comp. can't browse other site using PPPoE Broad Band Connection

i have this 3 sets of computers the other 1 is a server which is already connected to internet using PPPoE Broand Band Connection. I already enabled the Internet Connection Sharing for the home network and configured the workstations/client PC. All of them can now access the internet but some websites wont open like yahoomail.com, hotmail.com, friendster.com etc. but the yahoo.com itself and the other links/websites can be viewed i can even connect to mirc and other instant messenger.

can anyone help me please T_T :confused: