Try this:
Go to Start menu > Run
Type in DXDIAG and then switch to the Sound tab.
In the middle of that window is a slider that you can use to adjust your sound acceleration. Try lowering it or setting it to 'None' and playing and see if that fixes it.
Once you're done playing, you should put your sound acceleration back up to Full.
@mods/admins
Though this question has been asked many times, the FAQ here doesn't explicitly say this will fix ending problems, but rather just sound problems. We should change the FAQ say this.