One more update. Sorry!
The volume OSD was still working after I had installed all the updates last night. However, upon restarting the laptop today, it has disappeared again. I believe it is one of the kde packages that were in the updates that is causing this, but I'm not sure which one, or what would fix it. Again, the buttons still function correctly it's just the volume OSD that goes away. I'll do some more fooling around tonight and see if I can't get it working again.
Ok, I'll stop rambling now. I feel like this forum has been my personal journal lately!