I agree with other posters who have reported that the latest version of Skype does not work with the Quanta Integrated webcam of the Dell LX502X (and other LX models). The version of Skype that does work with this webcam is 6.3.0.107. Just be sure to turn off automatic updates in Skype (tools - options - advanced - automatic updates). Even then, Skype asks you to update but at least it won't happen automatically and disable video chat in Skype.
The latest Quanta webcam driver that Dell has available for download (Windows-7 64 bit) is A00-1.0.1404.1005.
Conflicts with this webcam/driver have also been reported on Logitech forums after installing Logitech webcam software.