iTunes won't import/convert AIFF files with 5.1/24bit/48kHz

Hi,

maybe someone can help me. I have ripped a Audio-DVD with 5.1/24bit/48kHz to FLAC some time ago. Now I want to import them into iTunes. So first I tried Max and XLD and converted them to Apple Lossless format. But iTunes just ignores them when I drag them over the library.

Then I thought, maybe the converters can't handle the extra channels. So I imported the files into Cubase and converted them to AIFF.

Then the same procedure as before. This time, iTunes accepted 10 out of 14 tracks. Why the remaining tracks weren't imported stays a secret to me.

Now, since AIFF files aren't compressed, I tried to convert them to Apple Lossless from within iTunes. But this time it hits me with an unknown error -50. ***!

Has anyone experience with high quality files like this and successfully imported them into iTunes?

Thanks, Cold-1