The file does not have proper content to reconnect

Hi everyone

Before returning a rented mac used to edit a feature, I have copied all the project files, clips etc of the feature to an external drive and have brought it to my studio where I am checking that I can open the project on a different computer and there is nothing missing.

I went through the reconnection process as expected, however, a small number of clips gave this message: "The file does not have proper content to reconnect to at time in sequence . Click OK to make this item independent...."

I clicked OK for all the clips. These clips now show as white in the timeline and show the Media Offline message in the Canvas when the playhead plays over these clips in the timeline. Oddly, sometimes only the audio tracks of the clip are affected, sometimes both audio and video tracks and sometimes the video track only! And there are some examples where the video and 3 of the 4 audio tracks of the clip are affected.

Does anyone know what I need to do to fix?

The project was cut in FCP 5.1 on a Mac Dual Core 2.66 Intel and my computer runs FCP 6 on a Mac Dual 2.7 GHz PowerPC G5. The film was shot on HD but downrez'd to SD - DV Pal 25fps for editing.

Many thanks