Images missing after importing to catalog

[tylmaster]

When I import photos into a catalog (Ctrl+I), there are some files missing.

Current example:
851 photos in folder
-> import folder into catalog
841 photos in catalog

I had this problem with various catalogs and even much smaller folders where about half of the photos were missing in the catalog.
Reimporting doesn't help, still the same images are missing.
I don't get any error message.

Is this a known bug? Is there any log file to consult?