ABC Import plugin has suddenly stopped working

Hi,
I have imported a few small abc files without problems over the last week but when I tried again today I kept getting the message: File 'C:/Users/doug/AppData/Local/Temp/my_file.xml' is not a valid MusicXML file.
I have reinstalled the Musescore program (latest version from the Musescore site) but it hasn't helped. I have also tried to import ABC files from different sources but always get the same message.
I'd be very grateful for any help solving this problem.
Many thanks,
Doug