Broadcom Netxtreme gigabit Ethernet Problem.

My problem is very difficult and I cannot solve it when I buy a pc. That is my pc mainboard is an intel chipset i865gv with built in sound, vga, and a lan controller.My problem with Lan Controller which is Broadcom Netxtreme gigabit based it is not working since I bought pc when I connect internet through it then it says user name and password invalid but when I connect through an pci lan adapter my connection working perfectly.
Anyone reply but in detail.
Help needed for solve this problem.
Thanks.
