The problem I'm having is that at random intervals, my laptop stops passing traffic over the wireless interface. Windows still shows me associated to the access point, but no traffic makes it across the link. Eventually Windows will show "limited connectivity" on the interface. I have to disconnect and reconnect to the SSID in order to get things working again. This is the case on both the 2.4GHz and 5GHz SSIDs.
I just installed an AC7260 card in my laptop, running Windows 8.1 64bit. I'm now on version 17.0.0.34 of the wireless driver. I have a 4th-generation Airport Extreme AP, running 2.4GHz and 5GHz SSIDs. 2.4gig is running in b/g/n mode, and on 5gig I've tried a/n and n only modes, with both 20MHz and 40MHz wide channels. I've verified there are no other APs I can hear on the same channels I'm on. I have my wireless security set to WPA2-PSK. I've also tried setting the Airport's multicast rate to both low and medium.
As far as device settings go for the card, I have:
802.11n channel width for 2.4GHz: auto
802.11n channel width for 5.2GHz: auto
ARP offload: enabled
Bluetooth AMP: enabled
Fat channel intolerant: disabled
GTK rekeying: enabled
HT mode: VHT mode
Mixed mode protection: CTS-to-self enabled
NS offload: enabled
Packet coalescing: enabled
Preferred band: No preference
Roaming aggressiveness: medium
Sleep on WoWLAN disconnect: Disabled
Transmit power: highest
Wireless mode: 802.11a/b/g