Audio and waveforms missing in timeline

I've been running CS3 on a dedicated machine for a while now with only harmless errors. This is a serious one: I opened up a project the other day to find the audio in my timeline gone. Not the clips themselves - they were there (and video is OK) - but they play silently and all the waveforms display zero signal. This is happening to my DV clips as well as mp3 audio from an iRiver. The original clips in my bin are all fine. What is very strange is that even though I worked on this project for several days before this error occurred, all autosaves from the lifetime of the project reproduce this problem.

I tried to copy and paste the troubled clips to a new sequence as well as a new project, to no avail. The error travels with them.

I am currently working with clips from the same NTSC-DV cassettes in other projects, error-free.

I know CS3 has been experiencing a lot of audio issues. Anyone met this one yet?

Thanks,
Ian