We are having the same issue. Our ISP is not p2p throttling or packet shaping in any way that would affect gaming. They even came out and gave us a new (better) modem, new line splittlers, and checked all line signals from the street up to help us out. It is NOT on our end.

This EXACT problem happens ONLY when playing FFXIV. Every time we get a 90K, our internet (say someone else is using the net on another computer) stops responding as well.