A better question would be, "what predictions did Krugman make which disagreed with non-Keynesians that turned out right (or wrong)?"
Various ideological enemies of Krugman made these same predictions. All you are really saying is that Krugman, along with everyone else, gets the easy ones right.
Scott Sumner predicted the former as did most of the market monetarists.
Another great Scott Sumner prediction: fiscal austerity hurts if you lack an independent central bank, but not if you don't (directly contradicting new style Keynesians, e.g. Krugman). The results: http://www.themoneyillusion.com/?p=29692
Various ideological enemies of Krugman predicted the housing bubble, and far more clearly than Krugman; Ron Paul, for example, argued against the creation of a housing bubble in 2001. It's hardly clear to me that Krugman even predicted it. From your article: "To fight this recession the Fed needs more than a snapback...Alan Greenspan needs to create a housing bubble to replace the Nasdaq bubble." The wording is ambiguous, but to me it sounds less like a prediction and more like advocacy.
A few years back I was a solid structuralist, but the monetarists have a really good track record of disagreeing with other people and coming out right.
Calling the market monetarists ideological enemies of Krugman seems like an exaggeration. He's linked to and cited them favorably a lot (although he has basic disagreements with them.)
> Various ideological enemies of Krugman predicted the housing bubble, and far more clearly than Krugman; Ron Paul, for example, argued against the creation of a housing bubble in 2001.
I'm not qualified to adjudicate between Krugman and the market monetarists, but I feel it is important to realise that many (and many prominent) people did fail to make these predictions, and essentially all of them have kept their jobs and their status.
http://news.bbc.co.uk/1/hi/business/8081813.stm
Semi-prediction of a housing bubble (August 2002):
http://www.nytimes.com/2002/08/02/opinion/dubya-s-double-dip...
Inflation and interest rates will remain low in in spite of stimulus and QE (many times).
A diagnosis of potential problems with the euro, many of which have come to pass (2001):
http://web.mit.edu/krugman/www/euronote.html
This is by no means an exhaustive list, but it is quite hard to find a major misstep that he has made as a direct result of his Keynsian beliefs.