The problem occurs when you select "Items since last import" OR if you individually select each item that is new, however if you choose the latter it only freezes when you have finished selecting all of the new items since last import. It seems to freeze on the last one you select regardless of which item you select last.
Therefore a fix is to take a spare photo before you import. Then select each of the new items you want to import, excluding the spare, and you will be able to import them. Of course it's not a very helpful fix if you have large numbers of photos as it would then be impractical to manually select each one, but for smaller imports it works fine.
I guess there's a link, but there's an bug before you even get to this. The import button shows displays "Import x of y items" implying that this will import all x new items. But the selection option is defaulted to "None" and no items are selected by default, so clicking this button without making any selections first will import zero items (i.e. do nothing), not the x new items as the button text implies. The previous version pre-selected each of the items since last import by default, which was much more satisfactory.
Even more irritating is the fact that the option to delete photos once imported has gone. It was bad enough that we couldn't set this as a default, but not being able to force it to delete them at all means you have to manually delete them on your camera after importing. I forget to do that which is the only reason I need the option to import items since last import rather than just importing all of them.