Astrid Elke Witte 

Did you check this option before creating your project?

Hi Paul, Thank you for your reply. Sadly, this did not work. I selected the option highlighted before setting up the new project (I actually wanted to re-use the existing, old project, but realised that I shouldn't when you posted) so I set up a new project, which gave the same error message upon importing the IDML file (it is actually an IDML file, only Studio treats it as an ICML file). Best regards.

The same happens if I tick the option concerned under "Adobe InDesign CS4 CC IDML".

Astrid Elke Witte 

Astrid Elke Witte said:

(it is actually an IDML file, only Studio treats it as an ICML file)

Really?  I think you need to look at that.  There are separate filetype foe IDML and ICML, they are not the same thing.  ICML files are handled with InCopy and IDML with InDesign.

Astrid has ticked the option concerned under all the Adobe DTP file formats in Options and that did the trick. She got the IDML file into Studio and handed me the resulting SDLXLIFF, which I could add to my Studio project. Best regards, Sebastian Witte

Astrid Elke Witte 

If in doubt check everything!!  Glad it's working for you now, but I'd still take a good look at your files and try to understand why it didn't work the first time.  Just for peace of mind.