I have a new "UNO" R3 which seems to run a pre-loaded "Blink" when attached to the USB port, but I cannot for the life of me get a driver to load so that I can use the IDE. The UNO is enumerated as "USB2.0-Serial" and no driver loads, so I can't use the IDE with it.
Help??
--Terry
Dr. T. Rowe
I think that indicates it has the CH340 USB-serial chip. You can find the drivers at the manufacturer's site here:
Just a quick comment - I'm a newbie and found this driver problem out the hard way. I got the "USB 2.0-Serial" listed in "other devices" in Device manager on Windows 8.1 and eventually got the right driver installed by letting Windows find the drivers online through the Update Device Driver option in Windows Device Manager. I usually disable this as Windows has a habit of installing updates that break the system whilst it's doing Windows update.
Good to know where I can get the driver directly next time (Windows found the correct one this time, and it is the CH340 driver you cited above.)
Funny how Google completely failed to find your comment, and it was only when I thought I'd post my findings in the community, signed up then searched in here that it showed up 
Murphy's search law in practice!