no idea but i'm pretty sure that this is a libmagick internal problem. if you don't need ImageMagick support, you could try disabling it in Gem's configure.
mfgasd IOhannes
Thanks IOhannes,
Without ImageMagick (./confugure --without-ImageMagick) everything works fine.
So my question now is: ImageMagick is used only for various image format import?
ciao