Solved this by using USBDeview by NirSoft.
There might be other tools around, I do not intend to advertise it, but it actually did the job in this case.
The problem was the only driver Lenovo lists, when select Windows 7 as OS. I've installed it, it's the Lenovo System Interface Driver and has to do with the softkeys, like monitor-switch, wlan-features, etc. on F1-F12.
Somehow, when installed, it tries to install the AuthenTec AES2501B device, which seems to be the fingerprint-sensor. However, it starts to switch constantly between active and inactive state, and that is why the device manager starts flashing and creating disconnect sounds.
The solution was to use USBDeview to remove the AES2501B and other suspicious USB-devices, which were not listed in the device manager anymore. Then found out that the AES would come back on every use of a shortkey.
I am still working on the proper driver installation, because now, whenever I use a shortcut key, this behaviour starts again.