A bug was reported yesterday in the Windows COM/ActiveX Personalization Library version 2.1.0
The private ID could get overwritten when setting the secret key. Setting the key first and then the private id did hide the problem.
yk.ykUID = ...
yk.ykKey = ... The UID was overwritten
yk.ykKey = ...
yk.ykUID = ... The UID was written correctly
This workaround is okay, but we've uploaded an updated version 2.1.1 today at http://www.yubico.com/developers/personalization/
Hardware- and firmware guy @ Yubico