1) Another round of quantitative easing (Fed increases the money supply) This will lead to a dollar collapse, or at the very least, a severe dollar devaluation, which is generally not good for the economy.
2) Fed raises interest rates. With higher interest rates, more people are willing to buy treasuries, and so, there's more money coming in to pay the bills coming due in 2010. Higher interest rates are generally not good for the economy, particularly if it's already sick.
3) US Government engineers a stock market collapse, to send people scurrying to the safety of treasuries (and thereby allowing government to borrow what they need to). Of course, stock market collapses are generally bad for the economy.
So, in summary, I'd say they are predicting that the U.S. economy will have a rough 2010.