There are two good reasons for thinking that Lenin did not write that sentence.
First, executing the following search on Google:
"present crisis" capitalism error site:http://marxists.org/archive/lenin/
yields no pertinent result. This suggests that nothing exists on MIA that is similar to the given sentence. Of course, that also might mean that my Google search was ill-conceived, or that MIA does not have the pertinent source in an electronic format. Probably, however, MIA has uploaded most of Lenin's collected works.
Secondly, Sen noted in his FT article that:
"Exactly 90 years ago, in March 1919, faced with another economic crisis, Vladimir Lenin discussed the dire straits of contemporary capitalism. He was, however, unwilling to write an epitaph: 'To believe that there is no way out of the present crisis for capitalism is an error.'"
This suggests to me that Sen had in mind a particular article, letter, etc., that Lenin published in March 1919. But Sen clearly states that Lenin wrote no such thing is the source material he considers. Sen, as a bourgeois critic, often makes some good arguments especially with respect to questions of gender oppression. Other times, like in the FT article mentioned, he is an apologist for capitalism. But in no case is he sloppy.
epoliticus
-- "In the tender annals of Political Economy, the idyllic reigns from time immemorial ... the present year of course always excepted." -- A German refugee, circa 1867 --
http://epoliticus.wordpress.com/