Sounds to me like you have a cheap audio card. Even with alsa if your card doesn't support hardware mixing then it can cause problems when you load PS. I know you can enable software mixing to get around this but I forget how. I'll have a look around later when I have more time though and see if I can remember the procedure (or find it on google).
Update: Enabling software mixing is easier than I thought now. It used to be buried in a config file but is now accessible through the gui.
Click on the menu Systems and go Preferences ----> Sound
Once there you should see a screen like this:

One of the tabs should be labeled "Sounds". Select that tab and you should see the following:

Make certain that "Enable Software Sound Mixing" checkbox is checked. If you still have the same problem or that checkbox is already checked, fling another post this way and we'll see what we can come up with.
Update Update: I'm not sure where this is in the KDE menu system, but you should be able to at least find something similar. I'll see if I can find any KDE docs on this.