OK, that's just plain weird, but after your banana/plantain post-it episode (That still makes me laugh) I'm beginning to believe anything from you is possible.
However, one thing that might be nice to try, after you've recovered your precious recordings (Why the duplications in HD and SD, surely HD is sufficient?), is if you can write to the NTFS HDD. If that writes and reads succesfully, as you have with your TV recordings then that truly is the magical, mystical altar of a hybrid drive
Personally, I think the early part of the HDD, where all the partition gubbins and other stuff is held, has gone truly wonky. The EXT2 capable PC see's what was there because PM8 didn't delete it, just tried to change the gubbins and failed, whereas the non-EXT2 capable PC just assumes it's a normal drive (And blows a woobly when you try and use it).
Did any of that make ANY sense?