I have the exact same problem and started googling around found this thread.
I had the same happen: very high latency when downloading at high ~100Mbps speeds using utorrent.
And behold I solved the problem! Updated utorrent from 1.8.5 to the latest 2.0.4 (Build 21586). Also i unticked "Disable windows caching of disk writes/reads" from disk cache options. And now the lag is gone
I'm not sure unticking the settings were the key, but I wont dare to touch anything now. It would make sense, that having windows caching disable could cause an immense amount of interrupts.