我以前也是一样的问题，后来问了computer center得到的答案是：

1. Click Start , point to Settings , and then click Network and Dial-up Connections .
2. Right-click the appropriate dial-up networking connection, and then click Properties .
3. Click the Networking tab, and then click Settings .
4. Click to clear the Negotiate multi-link for single link connections check box (if it is selected).
5. Click OK , and then click OK .
6. Double-click the connection, and then click Dial .
o If this procedure resolves the issue and you can establish a dial-up connection, you do not have to follow the remaining steps in this article.
o If this does not resolve the issue and you cannot establish a dial-up connection, go to step 7 to continue to troubleshoot this issue.
7. Right-click the connection, and then click Properties .
8. Click the Security tab.
9. Under Security options , click Allow unsecured password in the Validate my identity as follows box, and then click OK .
10. Double-click the connection, and then click Dial to verify that you can establish a dial-up connection.

然后就一切ok乐，希望你的也是这样。