When my camera was able to use the USB cable connection and download directly from the camera, the "Safely Remove" in Windows never showed the camera in the list of devices that could be disconnected and dismounting wasn't needed.

A card in a reader usually will need to be dismounted before disconnecting, since the card/reader is just like a flash drive or external hard drive to the USB.

Failing to dismount can cause corruption of the USB controller in your computer. The recommended solution, according to Microsoft, is to disconnect all USB devices, and then get into Device Manager and DELETE all the USB port connections. The removal of the ports isn't "recorded" until you shut down and restart the computer. After you restart, plug the devices back in one at a time, allowing each device to be recognized before going to the next device. The OS PNP will create a new port for each device as you plug them back in.

The problem with this recommendation is that the ports to be deleted are shown in Device Manager only as "Port #" and it's difficult to tell what device goes with which port - and the number/device association seems to change sometimes when you reboot, posssibly depending on the order in which the OS PNP recognizes and remounts the devices during the boot(?). If you delete the port for both keyboard and mouse, it's really puzzling how you're expected to manage to delete the rest of them and properly shut down the computer for the reboot. Microsoft doesn't have a recommendation for this little glitch. (Even if you use a "wireless" mouse and/or keyboard, they're still mounted as USB devices in the USB controller.)

John