Driver of your sound card does not support smooth control of playback speed. When output sound by means of DirectSound the sound is sampled by tuner ADC (analog/digital converter), then transfers to system memory over PCI, PCI-E, PCMCIA or USB bus and after that converts back by DAC (digital/analog converter) of sound card. Because there is always difference between ADC and DAC characteristics, sound will lag or leave behind video. Clicks and stutters are heard during forced synchronization of audio and video streams, when time difference between them exceeds certain threshold.
Try to update sound card driver. If you'll fail to find proper driver, use sound playback over audio cable through analog audio output of tuner. For this you must connect audio cable to proper input of sound card and select correct settings in application. When audio cable is used there may not be any desynchronization because the sound is not sampled and not passed through PC and software engines and transfered directly to sound output of audio device.