I don't think I have ever seen that "too short" message for a lib but it would be worthwhile to check any info you can find on it. For example, mine in Slackware 14 w/ KDE 4.8.5 looks like ----
libnepomuk.so.4 modified Aug. 7, 2012 and is 904.4KB.
If you are a die hard file manager user like me you might ask, just how can I check such info when my File Manager (Dolphin) is not working? Obviously you could just use CLI and that's a good start. First of all "/usr/lib/libnepomuk.so.4" should be a link to the "real" file, "/usr/lib/libnepomuk.so.4.8.0" (on my system) your version will be appropriately varied. So first use
to verify that it is a link and to what version.
If you want to know the size you can use the "ls -hld" command but don't use that on the link because it will just report the few bytes that comprise the link. Instead, use it on the "real" file it is linked to. In my case it is
ls -hld /usr/lib/libnepomuk.so.4.8.0 |cut -f5 -d ' '
Incidentally the command reports a slightly lesser size than does my filemanager. In this case 905K, so it may round up oddly.
While I have learned to like Dolphin well enough, I also routinely install Krudsader
a really sweet Kde-based file manager that has many deep features that Dolphin does not. Since it grew out of Konqueror it has no need of Nepomuk.
I hope one or both of these methods helps you restore Dolphin as well as your sanity :P.