Snake Doctor

I'm using smart ripper to rip the dvd's I bought, and then importing the VOB files into vegas to render them.

This worked fine for the first couple of dvd's but now I'm ripping the files, importing them, and there's no audio track attached to the vob file....so my rendered files have no sound.

The DVD's however do have sound (played them to make sure)

Can anyone help me with this?

Thanks