We have tested the USB 2.0 Loopback plug under both 32-bit and 64-bit Vista Beta 2.
The USB 2.0 Loopback plugs can be used on 32-bit Vista.
The security requirements under 64-bit Vista are more stringent than 32-bit Vista and as such all kernel level device drivers need to be digitally signed using a new mechanism for Windows Vista. At this point in time, the USB 2.0 Loopback device drivers are not digitally signed for Vista.
If you want to use the current (2.0 1002) device drivers on the 64-bit version of Vista Beta 2 on a test system, you will need to disable this security check by:
(i) start Vista with "F8" and select "Disable Driver Signature Enforcement" or
(ii) run the BCDedit tool from an elevated command prompt (ie. explicitly right-clicking and selecting "Run as administrator")
Bcdedit.exe -set nointegritychecks ON