https://bugs.freedesktop.org/show_bug.cgi?id=32422
--- Comment #13 from Veli-Jussi Raitila vjr@iki.fi 2011-08-12 09:34:01 PDT --- I've had this same issue for ages on X1400. I has been seemingly random, but always with large images. With this one I can finally reproduce it reliably! Just pan around the xkcd-image for a while, keep switching between tabs and it will happen eventually.