RT-N66U Crashing when 2x EA-N66 are connected to it

Hi,

Long time reader, first time poster...

It took me a while to find the problem but when 2x EA-N66s are connected to my RT-N66U at 5GHz the router randomly locks up.

Performance is perfect though . Tested 35-40MB/s file copy speed in Win7 (pc 8 meters away from router - one wall in between).

I tried all firmware starting 220, 246, 252 and 254 + some of RMerlin's, even TomatoUSB.

Any ideas?

inspirit