I've tried both of those suggestions and nothing worked. What's strange is that I booted up this morning and the camera and mic were detected for a short time, then when I tried to use them it went back to "unknown device". This is not just for one device. None of the my USB device (external hd, cam, flash drive) are recognized.
Like I said, when I disable "USB2 Enhanced Controller" in device manager, everything magically installs, but operates at USB1.1 speed. USB 2.0 is also enabled in the BIOS so I don't know what's going on. I tried the Dell Chipset drivers too... I've attached a screenshot of what I see in device manager. The two "composite devices" are my mouse and keyboard which seem to work regardless of the problems.