shotwell doesn't render previews of images on a pendrive

I have my Nokia N900 in mass storage mode and both, GNOME Shell and nautilus ask me whether I wanted to use Shotwell to manage the photos on it. I do, but Shotwell doesn't render any previews for theses pictures,

ProblemType: Bug
DistroRelease: Ubuntu 11.10
Package: shotwell 0.11.4-0ubuntu1 [modified: usr/share/glib-2.0/schemas/gschemas.compiled]
ProcVersionSignature: Ubuntu 3.0.0-13.21-generic 3.0.6
Uname: Linux 3.0.0-13-generic x86_64
ApportVersion: 1.23-0ubuntu3
Architecture: amd64
Date: Mon Oct 24 19:01:22 2011
InstallationMedia: Ubuntu 11.04 "Natty Narwhal" - Alpha amd64 (20110201.2)
SourcePackage: shotwell
UpgradeStatus: Upgraded to oneiric on 2011-10-17 (7 days ago)