Unexpected USD strength in the last few hours

Has anyone noticed the incredible run of the dollar in the last four hours? From 02:30 to 06:30 EST:

USD/JPY: +100 pips
USD/CHF: +80 pips
AUD/USD: -80 pips
USD/CAD: +80 pips

I rounded the gains to +/- 10 pips, but you get the idea. The only currency still holding its ground against usd is gbp. It baffles me that I do not comprehend the forces behind such strong moves. Has the market simply gotten tired of selling the dollar and decided to buy some, for a change? I look at the same economic calendar just like everyone else but there seems be no obvious explanation for this rally - what am I missing?

Exhaustion, fib extensions hit in some cases, end of the week profit taking, those are just a few of the reasons I can come up with.

Edit: Forgot to add that a couple of major banks, JP Morgan and RBS, now project an ECB rate cut in the near future.

It's friday, a lot of specs will be closing trades for the w/e, especially after a week like this one. But the size of the move is not all that unusual...