I was hoping that someone else has run into this issue. I recently upgraded a WiSM controller for a customer from 5.1.163 to 6.0.196. Before the upgrade they did not report any issues with their clients, the majority of their clients are Apple laptops or iPod touches. After the upgrade I am running into issues with some of the clients. One specific client, running MAC OS 10.5.8 will disconnect from the WLAN and won't reconnect unless rebooted. I've run debugs when the client disconnects and I don't see anything happening on the WLAN to kick the client off the network. The client isn't idle and is running off of AC power and not the battery.
The customer had actually run into this issue when attempting to upgrade last Christmas break (Its a school district) and ran into similar issues and contacted TAC without a resolution. I'm leaning toward this being a client issue but I was hoping that someone else having seen this issue and found a fix for it, be it a configuration change or a client issue.