Port 80 (external) blocked under heavy load?

[rbailey64bit]

Here's a strange situation I've been unable to figure out. I have thirty MSM422 connected to MSM760 controller. They work great most of the time, but if under a heavy load (18 or more clients per radio) they stop passing external traffic over port 80. When this happens, I can open a command prompt on one of the clients, and successfully ping the external IP address, and name resolution still works, but I can't access any external websites via a web browser. If I restart the AP, everything works fine again. Internal websites continue to work.

Has anyone else seen this behavior or have any ideas what could be going on?

Software version: 5.5.0.0-01-9514

Hardware revision: B:48