I'm also struggling with this. In an attempt to Import From Catalog both image files and History states, I am having the two recurring problems below. Part of my trouble is operator error, I will bet.
1) Image file corruption. The Corruption presents as images entering LR with large areas of white containing colored lines, or as "Lightroom Cannot Import The Following Files" (no explanation given.) If rather than import from catalog, I simply drag the images (those described in the Import Catalog) into LR, there is no corruption or import failue - but I of course loose all the history states.
2) During Import From Catalog, the images files can't be directed to the folder architecture I intend. Instead the files continue with the architecture used in the Source Catalog folder - like "Source Catalog/Pictures/2009/2009-10-14". What I want is for the images within that 2009-10-14 folder to be copied to Destination Drive/Images/2009/2009-10-14".
If I understand Neil correctly, I can manually copy the source catalog files to the destination folder of choice, and then Import From (Source) Catalog to import the history states for those files. If that can work, I might get around this corruption issue, and also locate the image files as intended. Am I on the right track, in your views? Is this import corruption and failure commonplace? (OSX, LR 2.5).
Many thanks,
John Caldwell