Hi Mixx, I'm not sure what could be causing that error, but it seems that GTK is not working for a lot of people. If you don't mind, could you try uninstalling Python and installing an older version that should work better:
http://www.python.org/ftp/python/2.6.6/python-2.6.6.msi
http://ftp.gnome.org/pub/GNOME/binar...in32-py2.6.exe
http://ftp.gnome.org/pub/GNOME/binar...in32-py2.6.exe
http://ftp.gnome.org/pub/GNOME/binar...in32-py2.6.exe
I've pushed out Kindelabra v0.2 now. My program now supports DRM-d books.