M4A Tagging problems

I have a few M4A files downloaded fro a site called Beatport. Having a tricky time tagging them. From memory, I think at first I could not tag them with MP3Tag, then I could with a new release (can't remember which), now I can't again. If I look at the files in MP3Tag, they are displayed correctly. But any editing blows the tags away and I can't re-tag. Also makes the tracks unrecognisable (as audio tracks - i.e. I can't import them) in iTunes.

Strangely though, I can edit the tags (of the original files) in iTunes. Anyone else seeing this behaviour? Any comments as to why appreciated.

Thx.

H.

You can send me one of the original files for analyzing - maybe I can find something regarding this issue.

Regards,
~ Florian

Sent ... It's 4M ... sorry, but that's the smallest file I had ...

I think there is something bad with the file.

Both foobar2000 0.8.3 and the current foobar2000 0.9 beta 4 refuses to open the file.

Best regards,
~ Florian