since you have done the MS fix, then it shouldn't be the problem...
i have a past exp with SD's brother -> MMC card (their spec is almost the same)
i have a branded card reader from one of the Card marker which can read all my 64MB, 128MB, 256MB SD or MMC card...
on day, i go buy a MMC 1GB card for my phone... the phone can read this new 1GB card, not for my card reader
but i still need the card reader for fast transfer of MP3, so i bring the card to service center for exchange.
the staff there help me to test the card for 2 time, format and copy file, everything good...
but out of good will, they still change for me
put the new one in my phone and format again, also ok!
in the end i try my luck to buy another card reader, and it solve the problem...
but i still cannot explain why the old card reader doesn't work...
64MB, 128MB, 256MB and 1GB card are using the same file system of FAT and they are using the same Voltage too...(that time only 1 voltage, no dual voltage idea yet...)