CheeseQueen452, I know you said you'd prefer not to make another user account, but if you did it wouldn't mess up anything for your standard account, or any other for that manner.
My suggestion would be to fire up PCC and create a test user, then switch to that account and assign one of the sounds that is being cut off. If it's cut off with the new account, then it's something system-wide we'll have to check. If it's played completely, we've got something else to build on.
You can delete the test account in the same PCC screen entirely, including home folder, etc., so you have everything cleaned up nicely.
By the way, I keep a test account just for the screenshots and other stuff, because my standard account is in German. Switching users in KDE4 is easy and works great. I can get back to my own user account with <ctrl><alt><f7>, and to the test user with <ctrl><alt><f8>. When I log out the test user, I'm automatically returned to my standard account and everything's back to normal. A great way to check different scenarios.
Just a proposal from my side...

EDIT: I just remembered Tex suggesting turning off
PulseAudio in PCC. This solved several sound problems for me in the past.
Go to
Hardware => Sound configuration, uncheck
Activate PulseAudio and click
OK. Log out and back in...