[kovidgoyal]

Run calibre in debug mode (right lcick the preferences button and choose restart in debug mode) and post the debug log after importing fails.

You can also run the importer from the command line, which might work better, like this:

In a command prompt:

calibre-debug -c "from calibre.utils.exim import test_import; test_import('c:/path/to/folder/with/exported/data', 'c:/path/to/empty/folder')"

all your libraries will be created inside c:/path/to/empty/folder

Note that C:/path/to/empty/folder will be deleted if it exists, so make sure it is empty/not important.