'llo here

I have a strange issue. My ROMs are set in letter folders (GB and GBC, and for each one A, D, C, etc"
My EDGB gives me an error 0xD3 just for the "D" ROM folder or the GB catgory.
I fully formated the SD card twice, uncompressed my ROMs a second time to get fresh new folders, and copied back to the freshly formatted SD card, and I still have the same error.
I'm right now formatting an new SD card...
What's that 0xD3 error, and why does it occur for the same named "D" folder, even when formatted and newly uncompressed ?