Card or Camera error? F30 1gb H fujifilm XD

I was videoing a school musical item when the camera shutdown by itself. I did not have my fingers near the power button - only on the side grip.

The battery read full and the camera powered up when I pressed the power button to restart.

I took other footage and stills but most seem corrupted after the shutdown..

This has happened twice - usually when the card is just on half full.

Any ideas? I can see the full images on the camera but not after downloading via card reader.

I reformatted the card and took more video without problem.