After upgrading to Mandriva 2010.1 64bit I noticed that my system (KDE, PowerDevil) wasn't switching profiles anymore if - for example - I disconnect it from the electricity. Profiles seem to be set right, and both acpi and plasma-battery can tell if battery is in charge or not (although I can't manually switch profile anymore as the dropdown list was removed), but even if I let the battery go down as low as 3% nothing happens. Even event sounds are not played.

I firstly noticed when I was logged in a shell (no KDE sessions open) and the screen got darker as the battery charge went down. Then I found no way to restore brightness other than operating the slide on plasma-applet, so I have no idea of which profile I'm on right now.

If someone could even just explain who takes care of managing profiles (KDE, the kernel itself, some module or demon, X...) that would still be quite helpful!

I don't have mandriva, but I'll assume that the front end to the power management system is the same (conceivably, it may not be, but most likely it is). And kde is some variant of KDE4, isn't it?

Some bits are done at various different levels, but KDE should provide the front end to control configure everything else. You seem to be talking about a laptop (correct?).

I had to define another profile, because, when on power, I'd never get suspend because even though the lid switch activated, on the performance profile (because it was plugged in) didn't do any power saving, but I really know nothing more than that.

Ops sorry, I thought I gave all the relevant informations but I obviously forgot some. Yes, I was talking about KDE4 (v4.4.3) and I'm on a laptop.
I didn't really understand what your suggestion is:
I already have different profiles:
Performance
Powersave
Aggressive Powersave
Xtreme Powersave
Presentation

but I can't switch manually between those (as the battery plasma applet that allowed to do so seems to have been modified since kde 4.3, at least on Mandriva).

Allright, just to be helpful to someone else having this same problem with the following symptoms:
- no energetic profile switching possible (either manually or automatically)
- suspend to ram/to disk doesn't work from KDE menu (but it does from command line)

it is signaled to be a bug in the update to Mandriva 2010.1
the solution proposed on Mandriva's wiki to give the speedboot=no option at boot time doesn't work (at least for me). What worked was a quick edit I found on some other website: http://forum.mandriva.com/viewtopic.php?t=129728
I hope this helps someone - the fix is very easy and worked for me. Even the dropdown menu in the battery applet has appeared!