Fingerprint scanner problem

[toothandnail]

I have a T61 with Vista Business installed. It has a fingerprint scanner which worked when I first got the machine, but at some time since, the fingerprint scanner has been disabled.

The problem appears to be software - I can go through the registration process and all seems to work, but at any login attempt, the reader comes up with a red dash and will not let me use it. I suspect it is something I have either done (or not done?), but haven't so far found any clue as to what I need to do to re-enable it.

Any ideas?

paul.