Make sure you're using valid sounds and sound formats.
Unrealed won't do a basic check when importing, even if incorrect.
Convert all your sounds to 22050 khz, 8-16 bit, mono and try again.
If your only Wav editing program is Windows' sound recorder, get Wavosaur, it's less than 1mb and actually looks like a sound editor.
Voice Pack Tutorial
Re: Voice Pack Tutorial
Thanks, I'll try that. Did you mean 22050 kHz or 22050 Hz? kHz seems quite large..