Somehow the Driver for the fingerprint-reader of my HP Compaq 6910p got broken by a recently Windows Update.
One way to restore a broken driver is to restore Windows to a restore point. If you just want to restore the last driver version follow this instructions:
Start >
Control Panel >
Type in the search box "Device" >
Click Device Manager >
Click Personal identification devices > (Or any other device group)
Click Authentec ‘xxx’ > (Or any other device)
Go to tab Driver >
Click Roll back driver