I don't know if this is a coincidence but after updating AP230's to 6.4r1 yesterday a lot of clients are having connectivity problems. In the event log I see a lot of deauthentication events but don't know the significance of that. On some older Dell laptops (Latitude D630) they indicate that they are connected but with no internet access. iPad Air has the connection indicator spinning endlessly. I had made some changes to radio rate settings for one SSID but have since changed them back wondering if they had caused problems.
If anyone has suggestions I'd be grateful to hear from you - I've got a lot of people suddenly unable to connect and have had to bring an older Sophos (Astaro) AP back online to limp along.