Binary package hint: grub
The original English version of the GRUB2 editing screen legend contains the vital information "Press Ctrl-x to boot [...]". It's even coloured yellow as to convey its importancy. The German translation of that legend, however, omits that information. In my opinion this is a critical bug as it effectively prevents the user from being able to rescue his system should the need arise.
IMPACT: As above. I've had to help several confused users unable to work out how to edit the boot menu and make their changes take effect.
DEVELOPMENT BRANCH: We picked up a corrected translation as part of a general translation update in Maverick. I've backported this one change from it.
TEST CASE: Install in German, and hold Shift while booting to display the GRUB menu (or, if in KVM, edit /etc/default/grub, comment out both GRUB_HIDDEN_TIMEOUT* lines, run 'sudo update-grub', and reboot). Edit a menu entry. Check that the legend includes a comment about Ctrl-x (Strg-X in German).
REGRESSION POTENTIAL: None that I can think of.