iTunes store previews on MacBook Air stop playing after 5-10 seconds

Mac OS and all relevant software up to date. All worked fine a couple of weeks ago but today when I accessed the iTunes store, any previews I listen to will only play for a few seconds. The play/pause icon still shows as playing but the song just stops. If I hit the pause button the song will resume but stop again after a few seconds. Have tried this on the iPhone and it is working properly there.