I have a Dell ultrasharp 20" monitor from a few years ago. It has an integrated webcam and microphone. I have used it for skype and haven't had problems in the past. I have used it with Starcraft 2 in testing the MIC function when holding down the "~" key. When I skype with it though, after a min or so, the person speaking through it sounds electronic. Like you are a robot. I have no idea if the MIC is broken since it works in the beginning, or if this is a function of Skype software or something. Any thoughts?
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It could be a conflict with another program like SC2. Try reloading the drivers for both to see if that clears the issue up. They should be on Dell's support site.