It looks like something wrong with the IPN server.
I had no problems before Jan. 24th when it was said IPN service would be upgraded. After that, it is very hard to connect to the server. And even if connected, it is very easy to be disconnected or the delay is too long to be accepted.
As for the dial-up, my wife uses dial-up access and has the same problem as I do.
But the weird thing is, my friend uses Bell Sympatico and she has no problems of connecting, but the quality is very poor for catching the words clearly.
Try ping ipnserver.online.sh.cn to see how fast the response time will be. Generally if there is no loss packets, the connection will be fine. If not, terrible. But as a whole, the service of Shanghai Online is so ashamed to be announced as "the Window of Shanghai".