I've never seen such an error, but I have an idea where it might come from.
German disk related errors in an otherwise English environment may come from Fat95. I think it defaults to German if you don't install another language. The volume name in all upper case might also indicate a FAT disk rather than an AmigaDOS disk.
If I continue this thought, you might have CF0 in Devs/DosDrivers and CardReset in S/User-Startup. Then during boot CF0 might be in the middle of reading the CF card when CardReset ejects the card.
