Hi Geoff
For starters, maybe my little demo will aid with a bit of
this.
Click
here to watch the demo
As far as previewing audio, are you using the Spacebar or F3
or clicking Preview > Play this slide or File > Preview >
Play this slide to watch the preview? If so, it's quite possible
you have managed to click the little speaker icon to mute the audio
during this method of preview. If you look between the Timeline and
the Edit area on the left side, you see a tiny little speaker icon.
If it's muted, there are no lines or dots on the icon.
Another thing that may be vexing you is found in the
recording options. Click Options > Recording Options... and look
at the Recording Options tab. Look at the last option. It is
labeled: Record actions in real time. If this is selected and you
wait 15 seconds before clicking an object or moving the mouse, that
time is then factored into the recording process and the slide will
then be 15 seconds or so long.
Cheers... Rick