Problems with SD card reader on Bootcamp (MBP 15" Late 2011)
Try to isolate the problem as much as possible first. 

Boot straight into windows (not thru parallels) and test the cards to see if they work. If they don't, the problem is with the driver inside w7. If they do work then the problem might be in the way parallels shares the hardware access with W7. 

When using parallels to access the hardware you are not using the actual drivers as you don't have access to the actual hardware, just a parallel's emulation of the hardware and an interface to it in osx.

If the problem persists in W7 reinstall the windows support files as it should work (mine works with SDXC perfectly), but this WONT fix the paralles problem. 

As I said the parallels problem is completely separated and much harder as you can't switch drivers. But try this: http://lifehacker.com/368819/access-usb-drives-in-parallels-and-your-mac-simultaneously

ie: add /Volumes as a shared folder (its where OSX mounts HD/USB/SD/DVD drives)