Well this is so old you may have already figured it out, but here goes - I just had the same problem, but found it because I had an iso image that would play just fine on the PC, but when burned to a disk wouldn't play on my DVD player. I got the "invalid UDF filesystem" message when trying to open the image in DVDShrink. So...I opened the image with Ultra ISO and noticed that there was no AUDIO_TS folder, just the VIDEO_TS folder. I added the audio folder, and saved the image with a new name. No more complaints from DVD Shrink, and it now plays on the home dvd player.