[Skunkworks] Stuck at disk is write-protected !!

It's a 2gb micro-SD loaded with games for my daughter's DS (using that R4 cartridge) It was working fine until last week when I tried to delete some files - got a nasty write-protected prompt BTW, the microSD is plugged into a cheap card reader (Promate crPro.2) and connected with USB I tried everything I found on the net, that is reformating disk (it refuse), trying to change disk letter (Ifeature not available) and I checked that "StorageDevicePolicies" value using regedit Still getting that nasty write-protection prompt. Any idea ?? Any help are welcome Cheers