Vista long-time network problem

My vista has the following problems:

I can't browse any web sites and connect to any IP/address through
IE,Firefox,CuteFTP and other TCP Protocol programs when I stared Vista over
about 8 hours in a sudden, IE repored "Can't find the server" in sudden, even
127.0.0.1 can't be visited.

But another XP-based computer can through Vista's ICS connect to the
Internet when the HOST computer can't connect.

The problem can't solve through disconnect/reconnect/log off, the only way
to solve the problem is restarting the computer.Reinstall Vista/Uncheck the
IPv6 Protocol is without effect.

A Windows XP in the same computer doesn't have the problem.

All of the UDP-based program can connect to the internet. No any report in
Event Viewer.

Network: ADSL (PPPoE by Vista), No virus detected by antivir.