For laptops that have the wireless display functionality (WiDi) like the Dell Inspiron 17R, there is an issue with a wireless IEEE interoperability requirement that won't let a device broadcast on the 2.4GHz band and 5GHz band simultaneously unless it's a certified wireless Access Point. (http://www.intel.com/support/wireless/wlan/sb/CS-031809.htm)
WiDi can only use a 2.4GHz connection so to prevent a laptop from also using a 5GHz connection while WiDi is being used they had to strip out 5GHz wireless connectivity functionality from the WiFi card on any laptop that has the WiDi feature.
