This is the response from Lucien of Cisco and I quote "The theoretical maximum is 2048. As part of 802.11, however, some number of these 2k addresses are reserved bringing the IEEE maximum down to 2007.
Although the AP motherboard has memory capable of handling 2007 users, the radio utilized in our 1200 Series AP has memory limitations which hold the maximum number of client associations to 255.
The number of 255 is active associations, though the cam table can contain 2048 entries because of the memory size, the number restricted for actual active association is 255.This number is still far too large for sensible networking but what is possible. Remember that WLAN is shared media, all users have to try to get access to the media by waiting until it is free and then sending a request to reserve the media for the duration of the frame size that they want to send. If the air is busy then you have to wait a random time and start again. So if you have too many users waiting they can end up waiting a very long time - sort of traffic jam effect at a congested unction, one more car and the traffic seems n times worse.I dont know as to how the number 255 was arrived at but it is largely irrelevant as 255 is still too large to be practical for active associations, we (Cisco) recommend 25-30 for most design work."
Another bottleneck you may want to look into is the switch and the WLC. Because you are using the 1140, it would be good that the switchports to your APs, WLC and uplinks are GigabitEthernet.
Hope this helps.
