Systems:
Dell XPS M1330
Dell Inspiron 1318

Problem: Changing power schemes from the drop-down menu in the Battery Monitor widget doesn't work. In other words, if I switch to the Presentation power scheme and set it to put the system to sleep in 5 minutes, it won't. The Screen section of the power management section still seems to function.
After several hours of changing preferences, creating new ones, and making my own power schemes, I restored the default settings and looked again. I opened the Battery Monitor widget by clicking (right hand, bottom) the wrench and taking another look. Under General Settings, Settings and Profile, there is a tab, Profile Assignment. For Example: When AC Adapter is plugged in, I can change it to Presentation and set the profile to put computer to sleep in 5 minutes and it works. IF YOU CHANGE YOUR profile from here, it does work.
I now have my KDE 4.3.5 setup back with profiles for Movies, Performance Extended, etc.
I did several Google searches and it seems that some changes may have been made in Power Management in KDE SC 4.4. Hopefully it will be fixed soon!!

As always, this worked for me but may not work for you. Please remember to backup everything when you make changes, thanks a lot!

Can you please check that your packages are all up to date, it is possible that the D-Bus interface of PowerDevil was changed, and the older Plasmoid is unable to use it, causing this to occur.

Thanks for responding. I have tried the following on both Dell laptops. (Dell XPS M1330 with Nvidia & Dell Inspiron 1318 Intel graphics).
I DID update all packages and they are up to date, i.e., Backports, etc. The I've done this install more than once and I do it in init 3 with apt-get dist-upgrade. With the Dell XPS I noticed that sometimes I had to re-run apt-get dist-upgrade with the (-f) command. Both times all packages installed with no problems. Two other times on the Dell Inspiron this didn't occur at all.
I've tried the following live CD's; Kubuntu Lucid (nightly build April 1), Chakra Alpha 5, as well as a full install of PCLiniusOS Beta 2 with all updates applied. All include KDE SC 4.4.1. OR 4.4.2.
Results: With all tested Distro's I've had the same results with the Battery Monitor Widget (or power control) that I'm having now. The drop down in the Battery Monitor widget still does NOT change the Power Schemes though the drop down menu. I'm not a developer but I wonder if the more pronounced bug where the Battery Monitor widget drop-down menu gets cut off or goes below the panel could have any connection to this issue.
I have to reiterate that KDE SC 4.3.4-4.3.5 Battery Monitor widget works on both Dells I have with no problems whatsoever. Making and using Power Profiles on-the-fly works easily and if I, for example, want to use the, "Movie," profile I created to keep the laptop running for up to 120 minutes before sleep (suspend) a quick change in the Battery Monitor Widget
works flawlessly.
Conclusion: This has to be either a Dell problem, which I doubt, or a KDE SC 4.4 bug of some kind. I know just by reading that changes under the hood occurred in KDE SC 4.4. Unfortunately, I'm just an average user that knows how to tinker with some preference files and use the command line sparingly. This problem I can't solve.
The D-Bus package that you speak of seems to be updated in Kubuntu Lucid, however, this does not seem to fix the problem. ANY further suggestions, command line options, etc, that I could try I would be welcome!
Thank you for your time...