It sounds like you have ungrouped the audio from the video, so when you do your cut on the video, audio is unaffected. When you are editing/cutting, make sure the video and audio objects are grouped. If they are grouped, clicking on one will also highlight the other. To regroup, click on one, hold down CTRL, click on the other (both will now be highlighted) then click on the chain link icon.
If you're still have trouble, post a screenshot of your timeline for us to peruse, and perhaps describe in more detail the actual steps you are taking.
Thanks Al. I tried group & ungroup but never got the audio display. I tried a 30" mp4 clip with some success but I think I need more memory. I am on minimum 4Gb, so have ordered bigger chips. I'll let you know if that works.