Well check the interference on the RAP
show ap active ip-addr <ap ip address>
Check to make sure:
• Channel Frame Retry Rate % is below 30%. If higher then too much interference.
• Channel Noise Floor is above 80. If Noise Floor is lower then too much non-802.11 interference
Another thing you should tell him
When he disconnect is someone is using a wireless phone? or an microwave oven near?
IF you see how much interference a wireless phone and a microwave oven do you will be REALLY surprised...I show this to clients always with a fluke airchecker i have and they get surprised as well...