Nokia 6300: “Memory card in use by another application”

I miss my old phoneToday when I connected my Nokia 6300 to the PC with the USB cable, I got the error message in this post’s title. The 6300 has not been a great phone for me (I miss my Ericsson W810i), but at least upload over USB had been painless until today. It’s full of really bad engineering like this:

When your background image is an animation that’s stored on the memory card, it will lock the memory card.

Yes. It seems somebody made the memory card an exclusive resource, and the code that’s playing background animations locks this resource. Solution: Reset the theme to factory settings. Upload podcasts again.