This may be cause by ARP-attack launched by malware in your computer.
Sorry, I could not find any English/ Traditional Chinese good anti-ARP attack software for free.
For Simplified Chinese software,
http://www.beike.cn/arp.html
Though the installation is unintelligible codes (you can click the buttons to install it)
the user interface is simplified chinese.
Hope this helps.
Please follow my answer at
http://tw.knowledge.yahoo.com/question/question?qid=1510061609790
to remove virus in your computer.
2010-06-18 11:52:19 補充:
Even if you have reinstalled Windows, network worms can easily reinfect your computer in a short time, even before security patches are applied.
Reinfection may be caused by other infected computers in local network.
Visit my blog for virus removal procedures.
http://removevirus.blogspot.com/