FC5 Thumbnails for raw files

[Antonio Montagnani]

I am using Ufraw plugin with GIMP.
Not long ago (in the FC4 times...) when I opened a raw file (PEF from
Pentax gear), when I closed GIMP a thumbnail was created also for a
PEF file.
Now, I loaded PEF files from my camera but I can't create any
thumbnail (representing the picture). There is no thumbnail of any
kind in the nautilus window (in the past I found the general
thumbnail before using the Gimp), while the old PEF files in same
directory have a thumbnail....
Any hint?

-- 
Antonio Montagnani
Skype : antoniomontag