[GraemeJ]

Thanks Graeme - the only bad thing about the problem being on the companion side is that the companion actually doesn't do any processing - it just streams the backup file over to the tablet, and the tablet uses almost the same exact code as when the restore happens only on the tablet. Time to start adding mp3 files to lots of songs to see if I can catch the error when it happens.

I did thnk Companion was actually doing very little, just hosting the file and then wirelessly transferring it.

From what limited information I can see, it would appear that the uploading of the backup (using Companion) is error free - the indication of pages being present is why I believe this, plus the fact that moving the whole backup file to the tablet and restoring from within the device is error free.

Which leaves us with what is happening when restoring through Companion?

I actually used a wifi link (Droid) to transfer the backup file to the tablet and this appears to be error free. I've done this quite often when beta testing and never seen any problems - in fact I use Droid nearly all the time for working between the PC and the tablets and never had cause to question it.

I guess Droid uses much the same wifi technology as Companion uses for transfer, but the latter seems to produce errors. I think that I would start my search with the transfer technology itself.

One more thing - I'm not convinced it's the presence of an audio file which triggers the error. Near enough all of the original missing files I had were only PDF's (and one text file) and nearly all of those had never ever been associated with an audio file.