I blogged about this on my site ...
So clients can throw bad mics and or packets get mailformed when it hits the radio. You will want to check to see if you have 1 client throwing these or different clients. Check the mac address of the client in the logs. This is also a way to create a DOS attack. There are tools to throw bad mics ...Not saying thats your case.
You can fix this in 2 ways.
1. Move to WPA2/AES
2. turn off counter measure
http://www.my80211.com/voip-labs/2009/12/29/configure-tkip-countermeasure-holdoff-timer-on-wlc.html
http://www.my80211.com/security-labs/2010/5/15/tkip-countermeasure-caught-in-the-wild.html
I hope this helps
"Satisfaction does not come from knowing the solution, it comes from knowing why." - Rosalind Franklin
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