Turning the Asus laptop with the 7260 AC card to 802.11g as well as turning off the 5Ghz radio on my router all 802.11b/g devices were able to connect. Unfortunately I'm no closer to determining the cause of my connection issues.
My Lenovo Win7 laptop with an Intel Centrino Advanced N-6205 connects to the 5Ghz spectrum w/o interferring to the other b/g devices w/o issue. Only the 7260 AC card operation causes issues.