Audio is disappearing

I am hoping someone can help me. I've scoured through the forums and tried everything that has been suggested in other queries, on the relevant KB page and so on - all to no avail. I have been using Articulate for some months with no problem at all, and this week it has all started to go haywire (just as we need to start publishing our tutorials!).

The audio recordings are disappearing as soon as they are made. They record properly (or seem to) and then when the slide is previewed, the sound is there. But when we go to synch animations, the audio disappears. It seems intermittent - some of the presentations lose sound and then the next day the sound is back! When the presentation is being previewed, something is playing as the right amount of time passes on each slide - just with no sound.

We are saving the recordings properly (as evidenced by the fact that the sound is there to start with), the ppta files are linked properly and are quite large compared to the pptx file, so I am assuming that the audio is there, it's just not visible! The audio editor is empty, even though the ppta file is large. The add-ins are all in place, I am using the harddrive, the software is up to date, there are no duplicate ppta files (not even hidden ones) - essentially I've followed every troubleshooting solution I could find, and it's still not working.

The error is also happening on two different computers.

Any suggestions?

Thanks.