Thats very odd!
I have the same Fireware and r4i card. Maybe it has something to do with the placing of the folders on the SDcard? But I suppose if it works fine on a different DS that cant be it... I just dont see what the problem would be if not a problem with the placing of the files on the SDcard.
Have you tried updating the DS?
Some people say it causes it to stop working, it may do the opposite for you!
I update regardless what the r4i people say... =w=