Comment 3 for bug 557606

Yes, I'm pretty sure it's due to the space. Temporary workaround is to make this change to /etc/grub.d/10_linux:

  - CLASS="--class $(echo ${GRUB_DISTRIBUTOR} | tr '[A-Z]' '[a-z]') ${CLASS}"
  + CLASS="--class $(echo ${GRUB_DISTRIBUTOR} | tr '[A-Z]' '[a-z]' | cut -d' ' -f1) ${CLASS}"

(I've committed such a change upstream and will backport it for the next grub2 upload to Lucid.)