Problem Fixed!
As one of the original posters noting this problem, I can also confirm (as has been confirmed a few posts prior to this one) that the problem appears to have been fixed. I had given up on trying all the suggested "fixes" and was content just to deal with this annoyance until Apple addressed it themselves. I now note that since upgrading to the latest iTunes, the problem with Finder is now gone. I can see the icons in Finder, and using the preview brings up the album art as well. I did nothing more than upgrade to iTunes so hopefully everyone else will have the same results. It's good to have things working as they used to.
As one of the original posters noting this problem, I can also confirm (as has been confirmed a few posts prior to this one) that the problem appears to have been fixed. I had given up on trying all the suggested "fixes" and was content just to deal with this annoyance until Apple addressed it themselves. I now note that since upgrading to the latest iTunes, the problem with Finder is now gone. I can see the icons in Finder, and using the preview brings up the album art as well. I did nothing more than upgrade to iTunes so hopefully everyone else will have the same results. It's good to have things working as they used to.