Some of my folders are in norwegian special characters (æøå). When I try to synchronize such a folder it can say that I have 152 new photos (all the photos in this folder) and that 152 photos are missing. When I use "Show in Finder" all the photos are ok. I don't like the folders to not be in sync, so I go on and synchronize the folders. Then I end up with two folders inside LR, but one is grayed out and contains 0 photos. I delete the grayed out one and continue to use LR. When I try synchronize folders right after this, it looks fine. But after a while the problem is back and I have to repeat the synchronizing. If I select "Update Folder Location" instead, the problem is fixed.
I use Lightroom 4.1 RC (but the problem was present in LR 4 as well). I have never used LR before, so I don't know about previous versions. My os is Mac OS X 10.7.3.