I am using the Android plugin for Eclipse, and when I try to run my program using a real device through the Android Device Chooser, my phone is not listed as a device. I have updated Eclipse, all of the Android packages, and the USB driver, but it still isn't showing up. My phone is running Android 2.1, which is also the target version listed in the Eclipse project.
Also it happens that the device shows up as an unknown target and the serial number as question marks as shown in the screenshot.
I just had the same issue with the Motorola Droid. I had 3 devices and only 1 was detected in the ADB. The one that worked showed up in device manager as "android adb composite interface" and the 2 that did not work showed up as "android adb interface". In Windows 7 I did the following.
If USB Composite Device doesn't show up then try browsing to the usb_driver folder in your android sdk directory for step 5 then try step 5 and 6 again.
Note : If Android does not appear at the top of this list as described in #2 and/or you find a device ADB with no drivers then you probably need to install the device driver, which in my case (HTC Glacier) was located right on my phone.