Comment 4 for bug 750592

MBybee, you have a different issue (probably an userspace one judging by your dmesg snippet, which is fine), as you don't have these errors reported here:

[ 1444.010900] mmc0: error -123 whilst initialising SD card
[ 1446.826514] mmc0: new SD card at address 1234
[ 1446.879755] mmcblk0: mmc0:1234 SA02G 1.83 GiB
[ 1446.882726] mmcblk0: p1
[ 1446.959734] mmcblk0: retrying using single block read
[ 1446.961019] mmcblk0: error -110 sending status command
[ 1446.961022] mmcblk0: error -84 transferring data, sector 391, nr 8, card status 0x0
[ 1446.961024] end_request: I/O error, dev mmcblk0, sector 391
...

If you still have the problems on latest natty, you should file a new bug report.