If you're running on Windows 7 it'll definitely be a driver issue. Not sure if you can get a Win7 driver for the 1DII...if not try the WinXP driver.
I've had similar issues with my 350D on Win7. Something else you can try is changing the Communication setting on the camera between Print/PTP and PC Connection. For tethered I have to have it on PC Connection, but for loading images into LR it only works in Print/PTP mode.
Darren