NEW YORK - Nearly three and a half years after the collapse of the Lehman Brothers investment bank, the Museum of Modern Art has mounted its first artwork devoted to the financial crisis: American-born artist Mark Boulos' video installation "All that is Solid Melts into Air." Nobody expects the MoMA to function like the evening news, but three and a half years seems like a very long time. Especially when you consider that last year, for the 10th anniversary of the 9/11 attacks, the MoMA mounted an exhibition about the terrorist assault that included no images of the towers being hit, burning or toppling. Is this reticence until we get the expression just right, or timidity?