Sorry but this is not that cause of your issue.
My pc couldn,t load windows XP Home when I installed external n/w card. The error message stated are "Mac Client Address xxx-xxx-xxx-xxx", where the "xxx" is a numbers. Currently I have a built-In n/w card in my motherboard, but it will hang when I connect to internet throught direct-connection, wherease the built-In n/w card works fine in a Lan network environment. My pc now is tested in a Lan network environment. Could anyone please tell me what was wrong and the solution for it? Thank you in advance..