This is a known issue to be fixed in the next update. Till then, don't click on the reader under Devices, but rather click on the same item under Drives in the LH side of the import dialog. It will load promptly.
It also seem to only generate preview of the thumbnail that are visible.IF I scroll the other thumbnail have no generated preview. So I cannot even et it create all the preview and wait 2 hours, I need to be there to scroll while it generates the previews