I had the same problem with my card reader. While this isn't an actual cure, a program called (appropriately enough) USB Safely Remove makes swapping cards and thumbdrives easier and faster.
You can download the shareware version here at cnet or at PC World if you want to test it.
This feature is needed when removing devices from either my built in card reader or front USB sockets. When I do so I find that neither the icon is on the tool bar nor are the USB drives in Explore. The only way I can retrieve them is by doing a restart. So at the moment I can only use a device once before needing a restart
Any suggestion why this is, and is there a cure for it?
I am running 32 bit Windows Vista Service pack2