I've erased all the fingerprint data in the BIOS, and reset the security chip (disable/enable). That cleaned up a lot of issues. Every so often, I lose all of my fingerprints. The first clue is the BIOS doesn't ask for a fingerprint on power on, then Windows won't show the fingerprint reader.
I can then re-import the data (backed up after a clean Win7 enrollment, got tired of registering all the time), and reboot. It will work for a while, but then something (unknown) will cause it to not work again. I will get several good reboots before this happens. I'm not sure if a Windows Update causes this, or something else.
I have been having this problem since I rebuilt my t500 with Windows 7 x64 about a year ago. Every so often, the fingerprint logon will stay at "Verifying" forever so I have to login manually using the password. Next time I lock the machine, the finger printer scanner is no longer an option. I can re-import my fingerprint and everything is fine for a while but I can not find a reason for this or a fix. Uninstall/re-install yields the same results.