My VirtualBox virtual machine freezes, when I try to use the webcam

I'm using a hp ElteBook 8540w with Windows 7 x64 as host and a Windows 7 x64 virtual machine running inside.

I added the webcam to to the usb filter:

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carefully terminated Skype ( 1 off the 4 mentioned ways works for me ) in the host to avoid accessing it the webcam.

Activated the usb device in the VM:
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When I click the allow button on http://www.testwebcam.com/
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The blue led by the webcam goes on and the VM freezes and can't be killed by taskmanager ( cf. here )

From this question I guess, that it is possible in some cases to use the webcam from inside the VM, but I didn't find out how to do it on my machine.

Edit:

Meanwhile I tried the same with an Ubuntu guest and have exactly the same result.