Question / Help Webcam green picture

[Mindfreak2]

Hello forum members.
I have a problem in OBS. My Logitech C270 webcam is not recognized. It only appears a green picture.
The webcam is functional because it displays a working video on webcam test pages.
Windows 7 (64bit)
Logitech C270
OBS (64bit)

 

[Mindfreak2]

The same problem with an older Logitech webcam.
Firewall and Antivir already switched off.
The cams are detected, but the screen remains green!
Does anyone have a hint?