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