This has happened only 10 or 12 times since you have had the controller?
It happened 10-12 times last semester, maybe more since I'm getting the reports second hand.
Can the client ping his/her default gateway?
Haven't tried that yet. We'll try it the next time we see the issue.
Are you sure that the client did not just fail authentication?
They are able to get on the internet and use it for a period of time, then they get disconnected for whatever reason and are not able to reconnect. Their wireless status still shows them as connect to the SSID,but all they can get to on their browser is the webportal. I've tried to reconnect them by logging in to the web portal, but I get the same results. After hitting login it returns you to the webportal page.
Do you have a custom login page?
Yes we have a custom web portal. The only modifications that I made were to the background image and the location of the login box. I moved it over to the right so that it wouldn't cover our School Logo.