Open the Windows Device Manger and see if your BlackBerry has a yellow exclamation point next to it. If it does, update the drivers. Point to C:\Program Files\Common Files\Research In Motion\USB Drivers.
Make sure that powersaving is turned off on your USB ports too, especially if it's a laptop you're dealing with (doesn't look like one by the screenshot, but maybe it is?) that can be found in the device manager under USB.
Also, make sure you have the actual handheld drivers installed. I know when I set up my new 8700r it wouldn't connect until I had the handheld drivers from rogers site installed on my pc (strange, I know).
Also this has been covered before if you are using a HUB for the USB connection many times it will not recognize it until it is directly plugged into the USB port at the pc itself.
Question, were you previously synching to another hard drive and have recently changed that? I know that causes this exact issue and files need to be removed from the registry before re-installing the desktop software.
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Now you can call me STORMin' Norman, except my name isn't Norman.