NDS-Card just emailed me and offered to send me a new R4i Gold, which makes me believe that there's no solution for R4i Dorasu rev C cards without the white dot.
Great service by NDS-Card btw. Hoped they would replace the "defective" card (it worked flawlessly for two months) but didn't expect...
I bought mine from NDS-Card. It is a rev C Dorasu card without the white dot. No update on a 3DS or a DS Phat and tried everything.
Fired several emails to NDS-Card. No answers yet.