I have been using my system for a while, and something triggered this to happen:
If I remove my SD card I can put it back in once or twice more and the computer will recognize it, but a lot of the times, if i try to reinsert it, it recognizes that a card has been put in, but it won't recognize the drive because of this code error found in the device manager.:
"Windows cannot load the device driver for this hardware because a previous instance of the device driver is still in memory. (Code 38)"
I have tried to uninstall the driver and it still does this? Any help because I have to restart my machine every time i need to insert another sd card.

I had the same problem. After cloning my hard drive and re-installing Windows Vista, I discovered that the problem begins after the install of AVG Free edition (version 7.1) anti-virus software. If you are using this software, just switch to different anti-virus software (or try a different version). Otherwise I suggest doing what I did which was to start with a fresh installation of Windows and check your memory drive for functionality after every install of software until you determine the culprit.