Alessia Vonau This is indeed a bit puzzling. Could you upload a sample file (anonymized content)?

I've solved the problem by creating a project in MemoQ, then I've exported the .mqxliff file and I've created a project in Trados with this .mqxliff file.
It works perfectly!
PS. the source file is .xlf (not xml.... I'm a bit confused!)

Alessia Vonau 

Thank you, I read that. But you also wrote this:

Alessia Vonau said:

Now the question is, is there any setting I would have done in Trados to avoid to use MemoQ in between?

And it is surprising that a comma in an attribute value should not be accepted.

yes, I know, but I think that the problem is not the comma etc but the file format.
Do you have any clue about the file format for Trados?

yes, I know, but I think that the problem is not the comma etc but the file format.
Do you have any clue about the file format for Trados?

Alessia Vonau 

I've done a lot with XML files, but the information I can glean from your post is not sufficient to understand what might have caused the error.