After playing with the Galileo I have noticed that some times the windows IDE will no longer be able to download sketches to the Galileo. I think there are a couple of failure systems.
If you notice that you cannot download sketch, AND you see that the COM port for your Galileo is still in the Serial Port list, even if you disconnect the Galileo then this problem can be fixed by un-installing the device driver, and reinstalling the device driver.
How do uninstall the device driver:
Open the device manager
Start-> Control Panel (on the right hand side of the start menu) -> Hardware and Sound -> Device Manager
Find the Galileo device
Expand the Port (COM & LPT)
The Galileo should be in the list
Right click on the Galileo device and select Uninstall
This will uninstall the device driver
When this is done, you can unplug the USB cable, and plug it back in.
The device driver will automatically install itself again (assuming that you did not check the Delete Software check box when uninstalling)
Let me know if this does work for you, or if it does not.