See this thread on the developers forum:
https://groups.google.com/a/arduino.cc/forum/?fromgroups=#!topic/developers/TTFiLcdXoSI

It sounds like the 8u2/16u2 chip that performs USB to serial conversion is not working on the bad board.

If the bad board is not even showing up in Device Manager, that is a good indication that chip is damaged or the firmware has been corrupted.

Here are the steps to try and use FLIP to reprogram the 8u2/16u2:
http://arduino.cc/en/Hacking/DFUProgramming8U2

It's interesting to note that motherboard has USB 3.0 ports.
There have been other reports of odd behavior with USB 3.0 ports. Most of the other issues have been with enumeration.

Anyway, glad you were able to get it resolved.

I highlighted the location in the image you attached earlier.

The preference panel image that you posted shows the location of your preferences.txt file.
Open the preferences panel.
Just click on the link and it will take you to the location of the file.

Make sure to exit the IDE
Then delete your preferences.txt file found here: /Users/<USERNAME>/Library/Arduino/preferences.txt
Launch the IDE

The issue you are seeing looks similar to this issue:
http://arduino.cc/forum/index.php/topic,50960.msg392328.html#msg392328

It doesn't look like he ever got a solution, except that he narrowed it down to some sort of PCI device helping to create the issue.

What version of Windows?
What service pack?

What does the error log say?

It there an application or serial monitor connected to the UNO when you shut down?

I am just grabbing at straws here...

Do you have any virus scan software or any other security software running while you are performing the install?

It possible that such software has opened the files to scan for a security threat while the setupapi is trying to perform it's job.

If you have such software, try disabling it while doing the driver install.

Press and hold the reset button, continue to hold while you select Upload in the IDE.
When the IDE shows Uploading, release the reset button.

Hold down reset and continue to hold down reset while you select Upload.
When the IDE shows Uploading, release reset.

No problem. Glad to hear you are up and running.

[folder]

The LED blinks because all the Arduinos are loaded with the BLINK sketch from the factory.

I didn't say anything about locating this file:  "ArduinoUNO.inf"

You need to select a folder not a file

Follow these steps exactly:

Look for Unknown Device under Other devices in Device Manager.
Right click the Unknown Device in Device Manager
Select Update Driver Software
Select Browse my computer for software
Click Browse button
Select the Drivers folder under the location of your Arduino software installation. (Do not select the FTDI folder inside the Drivers folder)
Click OK
Click Next

The Arduino IDE does not require .NET

The Arduino IDE is not really a software installation. It is just a zip archive of all the software.

You just download the software and unzip/extract it to a location on your system.  If you are unable to unzip/extract, then that is usually an indication the zip archive was corrupted during the download.

This is the link you should be using: http://arduino.googlecode.com/files/arduino-1.0.4-windows.zip

Have you guys heard of http://www.discourse.org/

It was started by Jeff Atwood from Stackexchange.com

I don't know much about it yet, but it does look interesting as a new take on forum software.