Some leading corporate executives worry there’s no economic engine available to drive growth in 2010: Technology, construction, finance — all sectors that have powered the U.S. economy out of the doldrums in the past — are flat this year.

And some boardroom denizens offer a bleak assessment: An economy that was driven by consumer overspending for years and by government overspending for the past year will have a tough time making any headway when the government support is withdrawn…

What’s got Wall Street even more nervous is the expectation that the commercial real estate sector is poised for a crash of its own, further dragging down the prospects of the national economy.