Curiouser and curiouser. Although I may have chosen a bad example, now that I think about it. A better test -- if you hold down the "mute" button, does the speaker system remain muted, or flip back and forth? (The experimental keyset should flip.)

Ah, so the buttons don't even light up? (Or give you that "tactile feedback" vibration, if you've got that on.) I guess it is something UI-related, then.

Hmm. I'm not seeing this effect on my machines, but then I'm still not testing on CSSU yet. (And yeah, everybody here has been getting on my back about that. ) I suppose it could be something CSSU related, although I haven't seen similar complaints from other users.

I doubt qtlockscreen would do anything. (If it did, it should be affecting more apps than just Pierogi...) Then again, I suppose I should ask -- are you seeing this only-one-button-works-effect with any other apps?

And yeah, the whole "portrait-mode-pseudo-feature" aspect of CSSU is very annoying for us folks who do want to lock our apps into a particular orientation. <petulant mode>I've even got "X-CSSU-Force-Landscape" set in Pierogi's .desktop file, but I guess it doesn't work nearly as well as the non-CSSU locking mechanism... You could try turning off "forced rotation", but of course nobody does that, because it is by far the most popular feature of CSSU, despite officially not being a feature of CSSU. </petulant mode>

Let me nose around the CSSU changelogs a bit. Maybe they'll have a hint as to some UI updates that might cause this effect.