Ok... I have been through complete hell today... All for nothing.
I had the same type of problem different solution...
Platform:
Windows Xp SP3 to Nexus one android
Problem:
fastboot-windows devices works; device driver succesfully loads and apearrs as Andriod Composite ADB Interface in the device manager. should work right... nope
Solution:
after several iterations using the correct driver. here is what finally worked for me. magic
1) allow android SDK to download driver
run android-sdk-windows/tools/android.bat
select the latest usb-driver, revision 3
2) in the device manager i selected properties for the android device bridge.
In the driver tab selected "Uninstall" and allowed the XP to reboot.
3) once shutdown, unplugged N1
waited (and waited) for XP to come up
4) plugged N1 back in
installed driver by selecting 'browse'
browse to the android-sdk-windows directory and select the usb_driver folder
5) start->run->cmd
run> adb devices
I also have the android-sdk-windows/tools in my path just to be safe.
6) pray
Driver info:
8/11/2009
2.0.10.2
not sure why its called rev 3 when not reflected in driver info