|USB devices may not work correctly when they're connected to certain USB ports, e.g. ports in a hub or on the front of a desktop case.|
See response 3 in this:
A thing people frequently forget to do (or are not aware of) is that when you want to unplug an external drive, or a flash drive, or a memory card reader that plugs in, or a memory card that plugs into a port on your computer, while the operating system is running, you are supposed to click on the Safely Remove Hardware icon in your taskbar lower right, and STOP accessing the drive you want to unplug. In XP it's a grey rectangle with a bright green arrow on it; in Vista, it's a small mid green circle with a white checkmark on it - it may be hidden - you may need to click on the < at the left end of the icons in the taskbar to reveal it. If you were accessing the drive at the time you click on the Safely Remove icon, you may not be allowed to STOP accessing the drive - in that case, access some other drive, then click on the Safely Remove icon.
If you haven't been doing that every time you unplug the drive, the data on the drive is usually not damaged, but sometimes it IS damaged, and in that case you need to use a program to repair the damage.
e.g. these suggested by aegis1 in a previous post...
No harm in trying a file recovery program. Depending on the amount of corruption, they can recover data with both FATs bad.
PC Inspector (freeware)
Zero assumption Recovery
The demo is limited
It will only recover 'up to' four folders per run
But you can make multiple runs
Really good, but you have to pay for it.
Re-formatting doesn't wipe all of the existing data from the drive - it makes it so the operating system or the phone doesn't know where it's located anymore, and marks the space the data was using as available for new data. You could try those programs or similar, but you were better off trying them BEFORE you re-formatted the card.