This is an issue with the pasteboard syncing feature between X11 and OS
X - please read the FAQ for a workaround:
"Copying and pasting in Inkscape creates pixellated images instead of
copying the vector objects "
<http://wiki.inkscape.org/wiki/index.php/FAQ#Copying_and_pasting_in_Inkscape_creates_pixellated_images_instead_of_copying_the_vector_objects>
hth, ~suv