Hi.
I have one AP (411AH) with 2 client, 5G turbo.
After I enabled the nv2 package on both clients, the connection losts, and they are playing permanent “connected-disconnected,ok” game. I can’t remote administrate the clients, becaulse all 22-50-st ping come back, and telnet, ssh not work.
On AP I can enable - disable the nv2, I can set any wireless protocol, I haven’t any connection with clients, or just this broken unusuable. Have I chanse to remot repair, or I have to go through the city 
?
No simple answer, it may be you have to visit city.
But one idea, try telnet connection to client? Telnet is more reliable for when remote connection is intermittent. Maybe, eventually, you get ability to tell client to change back to 802.11 mode. Manual makes it clear that best mode is to select “Wireless Protocol” setting to “Nv2-nstreme-802.11”. Not to immediately change a client to “nv2” mode only.
See http://wiki.mikrotik.com/wiki/Manual:Nv2#Migrating_to_Nv2