Comment 24 for bug 267682

Aha! Pitti, your xev output is not the same as mdz's or slangasek's, since it shows it (correctly) mapped to XF86Standby, which was the case with my Dell as well.

Slangasek says that removing ~/.Xmodmap (or creating a new user) helped make the keys start being recognized (although some still didn't function but for other reasons).

mdz, if you create a new user account and configure the same laptop layout, do you have the same symptoms?