Can you try to unplug the USB and then remove the device with the uninstall button?
Windows will ask you if you want to keep the driver or not. Choose keep.
Then reboot your machine.
Turn off the Galileo by pulling it's power plug.
Turn the Galileo back on and allow it to boot w/o any SD card (you didn't say if you had upgraded it, assuming not).
You need to give it a few moments, even after the USB led lights; there's not yet a linux driver at the other end.
Make sure you have no COM ports on device manger after it comes back up.
Give the Galileo another minute (this is alot easier to see if you have a serial console...) to get ready.
Then, and only then, should you try to make the USB connection.
Let us know how it goes then.
If anyone at Intel reads this; please consider putting a serial cable in the box, we need one!