WebCamTexture performance issue.

I am using a IDS ueye 3.0 camera with a WebCamTexture. All I do is play the WebCamTexture and map the texture to a plane in an otherwise empty scene. As soon as I hit Play in the editor the game runs for about a second, then freezes for 2 seconds and so on. It's not the cam playback that stops but rather the whole game freezes for this time. First guess was Im doing something wrong, but I verified my "code" with the internal cam from my macbook and it runs without problems. Now I looked into the profiler, which shows no spikes at all. At least nothing this bad and nothing related to WebCams turns up in the Hierarchy.

So just out of curiosity I switched on the Profile Editor option, and that is where it started to get really strange. Not only are there no WebCam related spikes showing, but the game runs smoothly. No stuttering at all. The only way to get rid of the stuttering seems to be to switch on Profile Editor. I also tried to build the scene and I have the same problems in the standalone build.

I am using Unity4.0 on Windows8. Any clues what this rather strange behaviour could indicate?