All frames dropped?

While exporting the film to my external HD, the usb port lost contact so the process was cut. But when reopening previously saved material all I get is a horrible sound and no images.

The message says: "One or more frames were dropped during playback, if this occurs freqeuntly try ...." I have the RT on dynamic, closed other sequences. Don't know how to lower the compression rate but I have the feeling that nothing of that will help since all frames seems dropped.

Anyone got any clue?

Yours dewjack