AirPlay on new Airport Express via NetGear at 5 GHz doesn't work

- New Airport Express (Model A1392) (7.6.4 firmware)

- NetGear WNDR3400v2

- Connected to 5 GHz network

- Analog miniplug cable to speakers

AirPlay stutters every half-second to a second, making it completely unusable.

Things I've tried:

- 2.4 GHz network works fine (except for the reasons I want 5 GHz anyway, e.g.: microwave oven interference, occasional drops from neighbors' wifi interference, etc)

- Ensure that on the Airport Express settings I'm using "Join a wireless network" and not "Extend a wireless network"

- Old Airport Express (Model A1294, with draft n) (7.6.4 firmware) connected to 5 GHz works fine. Only new Airport Express is having problems.

On NetGear settings, I have tried the following tips from reading other threads:

- Changing channels

- Ensure that "Enable Wireless Isolation" is unchecked

- Uncheck "Disable IGMP Proxy"

- Set "RIP Version" to "RIP_1"

- Uncheck "Enable WMM (Wi-Fi multimedia) settings (Unchecking this did work to get video streaming working on Apple TV though)

And so I'm at a loss. I can't think of anything else to try. 5 GHz is completely unusable right now. Anyone know of a solution?