Klite 15.6.8 Mega codec pack not working right.

I had 15.6.8 Mega pack installed on my PC and I'm using ConvertXtoDVD to burn my content and everything I burnt using 15.6.8 Mega plays like it's in fast forward and also sounds like a bunch of chipmunks when they are talking.

I reinstalled an older version of Klite which was 14.0.5 Mega and the problem is now fixed,I just wished I hadn't already burnt 58 wedding movie disc's of my friends wedding.

Why would this be the fault of K-Lite? I assume normal playback of your input files works correctly. ConvertXtoDVD is responsible for the conversion. It seems to me that it is making a mistake when converting the audio.
The fact that it works with older version of K-Lite might be simply due to a difference in settings. But ultimately, the bug is in ConvertXtoDVD.

How many audio channels does the input video have an how much channels does the output have?

You might be able to avoid the problem by configuring the audio output of the decoders.
Codec Tweak Tool > Audio Output > Stereo