Comment 8 for bug 790677

I played around and found out that this is somehow Xfce related. On both my computers mentioned above which run Xfce the issue is present, but at my friends PC running Kubuntu 11.04 64bit (so KDE, not Xfce) the feature works smoothly.
So I installed KDE on my computer and within KDE the specific inkscape feature works also smoothly; back to Xfce it doesn't. About Gnome I cannot tell, because Gnome nowadays somehow conflicts with Xfce, so I don't want to install it.

Hope that helps.