Sounds like you have an interfrence issue,
On the radio ports do you see a lot of CRC errors ?
Try another radio channel, use the acvtivity test to find the quietest channel.
Also use the antenna alignment test to get the best possible signal strength and quality.
Try these links for more details on how to troubleshoot this
http://www.cisco.com/warp/public/102/wlan/br-ts-22950.shtml
http://www.cisco.com/warp/public/102/wlan/rf-problems.shtml
David