Windows 7 Pro, tried it on 2 different computers. SDHC card reader on the one laptop copied images into LR4.2 just fine.
I think I found the problem through a long process of trial and error: a bad USB cable that came with the camera. When I swapped it with one I had been using with a different camera 40+ images transferred satisfactorily. I'll take another batch of photos tomorrow and verify.