When I booted up my thinkpad T60 yesterday morning and tried to use the fingerprint login I got the error message that the hardware was not connected, with only 2 months left on my warranty – it was looking like I was going to have to send it back.
Before I did that however I thought let me just run the hardware diagnostic PC Doctor, this did not find any problem so I downloaded all the thinkpad updates avaliable and restart. When the thinkpad came back on I logged initially had the same problem – but then if I gently swiped my finger on the sensor it worked.
I am not sure why the different updates sorted out the problem but it did. This is true in many case – if you are having a problem in windows for example – try downloading the updates first and seeing if that solved the problem.