Are you using ICE Normal or ICE Fine? ICE Fine blurs the whole image
whereas ICE Normal only blurs areas of "damage".
I say this as an LS40 owner (not LS4000).
Have you downloaded version 3.1?
I'm not going to suggest it will improve sharpness (unfortunately) but it is
considered essential as 3.0 is relatively buggy and does not get the most
from your slides.
Finally, when you scan slides, experiment with Auto Exposure turned off - I
think this gives better scans but so far there hasn't been much comment on
this from others here.