I had the same problems. What i did?
Download these drivers: http://www.ftdichip.com/Drivers/CDM/CDM%202.04.16%20WHQL%20Certified.zip
And follow this:
Open the Device Manager (type 'Device Manager' in the Start Menu' search box)
Look for the Leonardo in either "Other Devices" or "Ports"
Right-click in the Leonardo and select "Update Driver Software…"
In the dialog box, select "Browse my computer for driver software"
In the next box, select "Let me pick from a list of device drivers on my computer", and click 'Next'
In the next dialog, click "Have Disk" (you don't have to wait for the computer to retrieve the entire list)
This will open an "Install From Disk" dialog. Browse to your arduino installation folder (on my computer, it's C:\Program Files\arduino-1.0.1\drivers\Arduino Leonardo)Click OK.
Click Next (ignore any warnings about the driver being not digitally signed)
If a Windows Security dialog appears, select "Install this driver software anyway"
The dialog should say that Windows has successfully updated you driver software
Close the dialog and restart your computer.
After the restart, open the Device Manager again.
I hope that works for you guys!