Re: NXT USB communications
I removed the RobotC v1.40 and the NXT driver (again), reinstalled the XPsp3 driver from the RobotC.net downloads page, and yes, the NXT is recognized in Windows. The Device manager reports it just like the image you posted. The only thing slightly unexpected was the driver's reported date of 2/8/2006. I found this in the Device Manager | LEGO MINDSTORMS NXT Properties | Driver tab as shown below in the attached image.
Also, pursuing that one step further, the "Driver Details" from that tab points to a file named fantom.sys in this directory c:\windows\system32\DRIVERS. fantom.sys has Date Modified date of of 7/29/2008 at 2:09pm.
Not sure if that's all correct or not, but it's what I've got after a fresh driver install. Plugged the NXT brick in and it (again) says USB in the upper left of the NXT's lcd screen. Also, after installing RobotC v1.40 again I get the same error message. Nothing has changed. SW does not work after (3rd) fresh install.