All of sudden, since Yesterday, all clients were getting timed out and unable to brows. I did a ping tests from AP to radios, and it was consistently around 980ms or timeouts. I tracked down and shutdown one of the client radio, and everything returned normal, just occasionally hitting 650ms pings and timeouts.

I only have 8 UBNT NS2 clients on RB333/XR2 AP running on 5MHz Band.
In AP Access Rule (Access List), all AP/Client Tx Limit to 2M/400K or less.
For Data Rates, trying default, max 48Mbps and 36Mbps didn't make a difference.
I have latest firmwares on both RB333 and NS2.
RB333 CPU load is less than 13%.

Any suggestion would be appreciated. Thanks.