traktor pro won't play certain songs..Quick fix?

alright so i open traktor pro everything runs fine all my controls on vci work fine other songs play fine. Problem occurs when i open a certain folder of songs, i've played them time and time again but suddenly the wave form is greyed out and won't make sound when its playing. Also some of the loops i have in their preset work fine and are in yellow wave form color but as soon as the song gets past those it cuts off to no sound.
Any ideas on whats going on maybe a parameter problem or if anyones had a similar problem help would be greatly apperciated.
i'm running xp with traktor pro and vci100 no sound card is hooked up.