Who knows this error" m_ContinueWhenFinished == NULL "?

There are some tips here but it really depends on your specific code.

When dealing with WWW in C# I've found the only way to avoid this problem is to make your Start function IEnumerable.

     public IEnumerator Start(){
            if(sPost == null){
                 sPost = new WWWForm (); 
            } 
            sPost.AddField ("clientId", UserConfig.ClientId);
            WWW data = new WWW (sUrl, sPost); 
            yield return data;
            iHttp.SendMessage("DealNetData",data,SendMessageOptions.DontRequireReceiver);
     }