so you are saying that you had a Tranzeo with an Atheros chipset that DID NOT have this association problem, but when you take a Mikrotik with an Atheros chipset is DOES have the association problem?
hmmmmm.
to sergejs
You have to include more detailed description about the problem,
at least log information when clients are unable to connect,
wireless interface configurationl.
It is quite hard to determine the problem from the current description.
there is an entire post that was locked for some reason, the problem was never resolved.
http://forum.mikrotik.com/t/sr2-re-associate-problem/13306/1
I hope and pray that you are willing to help