Have to click "Switch User" for Fingerprint Reader to log me in

On Windows Vista, my Microsoft Fingerprint Reader will let me login with it
if I am not currently logged in. But if I am logged in and I lock the
workstation (Windows key + L), I cannot use the Fingerprint Reader to log me
in. It says "Unknown user" when I touch it, even though I am the same user.
So I have to click "Switch User", wait for my username to come up again, and
login with the Fingerprint Reader from there.

This does not happen on Windows XP. My friend experiences the same problem
on his Vista machine with the same Fingerprint Reader.

Is there any way to fix this without disabling the fast user switching
capability?

I am on Vista Ultimate, but I don't think this matters as my friend is on
Home Premium and has the same problem.

Is anyone else also experiencing the same problem? Try logging in with the
reader after pressing Windows key + L.

I'm having the exact same problem and have yet to find a solution as well...