after upgrade to 5.06rc on RB 333 power PC, Clients connected to AP 2,4G with UBNT card were offline. They were in registration list with theyr IPs, but you couldnt ping it…noone on interface 2,4G with UBNT card work, other iterfaces work correctly… Is there in 5.06 rc any problem with driver for UBNT cadrs? after downgrade to 4.16 all works fine.
anybody see, that winbox will crash if you press the ping button on client in registration list?
There is no such changes in v5.0rc6, and there should not be problems with the drivers.
What do you see in the logs for client, which are not able to connect?
nothing, all looked fine. clients conneted, signals OK, I could see theirs IP in registration list details, but couldnt ping it and internet didnt work too for they. after downgrade to 4.6 mikrotik all ok 
I thing that UBNT XR 2 have some problem? with 5.0RC? I have another XR5, I try it on another board when I will have a time