Found a forum where someone reported the same problem with skype, he too was advised to update the driver (like this):
You have to update your diver, but it's not the driver in "audio inputs and outputs" it's the driver under "sound, video, and game controllers"
1. Run Device Manager
2. scroll down to Sound, video and game controllers
3. single, left click the small arrow to the left. It will expand the "Sound Video, and game controllers"
4. Single click / select your audio controller -- in my case it was "Realtek High Definition Audio"
5. Now you need to tell it to update the software driver. I did this by selecting the 3rd icon in from the right. It's an icon with a small green arrow pointing up.
6. Tell it to "search automatically for driver software" -- Note: you have to be connected to the internet.
7. In my case, it found a new driver which was installed, and then the microphone worked
EDIT, oh, nevermind, guess it didn't help then