Crazytalk uses whatever sound card is set as default on your system. So if you have any other sound devices installed this may be the problem. You can check which is set to default by right clicking the little speaker icon (in the notification tray) of your task bar and then clicking Recording Devices/Playback Devices.
It would also be wise to make sure that your sound card has the very latest device drivers installed as this can also make a difference.
If you continue to have problems after checking the above I would advise you contact Technical Support using the link below. They will be able to investigate further for you.
Thanks and hope you get this resolved soon.