use routeros pppoe Server ,but xp pppoe clinet error 678

RouterOS General
1

I am use RouterOS 2.9.38 Pppoe Server ,but some client pppoe Client dialing Error 678 ?Please help me,thank you.

My compute use windows XP .

2

Please decribe the Error in Details. Also Send me the Configuration of PPPoE server. It will hel me top guide u.

3

Second result link explains the particular error,
http://www.google.com/search?q=error+678&ie=utf-8&oe=utf-8&rls=org.mozilla:en-GB:official&client=firefox-a