I have a Sandisk 8GB Ultra (30MB/s) SDHCi card, which is happily recognised by OSX by the built-in reader in 2011 Macbook Pro. However, when booting Windows 7 using Bootcamp on the same machine, with the same card, the card would not appear. By not appear, I mean neither (a) in windows explorer or (b) in disk management. I solved this problem by: Going to Device Manager, finding the Broadcom SD Host Adapter item, right clicking and selecting "Uninstall" and "Delete Driver". I then went back to Device Manager, and selected "Scan for Hardware Changes", at which point the SD card reader was found and a generic driver installed. Now Win7 happily works with this SD card. I believe this indicates something is wrong with the Apple bootcamp driver for the SD card reader in this particular machine, however the fix is easy. I'm making this post as I found very little (usually vague) information on the web about this specific problem, and felt this may be of use to others experiencing similar issues.