There's nothing in your config to suggest any limit on the number of client associations, however there are a number of bad practises on there that you may want to clean up in general.
Username = Cisco
Client VLAN = AP Mgmt VLAN
Using Static WEP = Very Bad
Still got all of the low-speed data-rates enabled
AP is on a massive broadcast domain, so performance is likely to be / get very bad
int dot11 0 channel not set
int dot11 0 power not set
int dot11 1 config is all over the place
The error message you posted suggests the client is opting to leave the AP, as opposed to the AP kicking it. What is the physical proximity of the AP & Laptops? Also, please please please make sure you've got the very latest drivers on your clients.