Arduino UNO USB not recognized I've just received my Uno today and already I think I may have broken it :(

I was able to connect to usb and upload a sketch (the blink). However, I then tried to connect a circuit to do the Hello World LCD example. After trying this a few times, I noticed the LCD chip get very hot...and I had mis-wired it. In any case, after a few more tries, the USB connection to my Arduino UNO stopped working.

I tried swapping the cable, connecting it to another mac and to a windows with no luck. I'm worried I may have shorted the USB bus chip when trying Hello World.

I also tried connecting a 12V DC power supply.

I still get the green power light and the amber L light...
Did I break my Uno?
How do I troubleshoot this one?
thanks
When the LCD pulled enough current to overheat, the Arduino's power supply (which I gather was the Uno's USB interface, at the time) was probably stressed to the point of failure. One fortunate result is that the Arduino took the hit instead of the computer's USB port that was supplying it. It's not clear which part was involved but here's a discussion on another forum concerning a similar failure and replacing the ATMegaxU2 which does USB-interface duty on the Uno (x = 8, if it's a rev 2 Uno, x = 16, if rev 3). It may be possible to replace the failed chip - regulator or USB interface (though with LEDs working, it's probably not the regulator). Otherwise, you can probably still program it with an ISP (In System Programmer). But the easiest way to do that is probably involves another Uno.