Hi Rudy,
I just tried with a 1242 running 12.4.21. It works as explained in the config guide.
I actually find the config guide to be better than the config example you gave : http://www.cisco.com/en/US/docs/wireless/access_point/12.4_10b_JA/configuration/guide/scg12410b-chap7-mbssid.html#wp1049591
Basically for basic checking you can just go with "ip redirect " in the SSID configuration.
It will redirect all HTTP traffic to the server ip you configured.
I just tried typing a non-existing ip "http://3.3.3.3" in my client browser and it took me to the server I had configured.
Are your clients using a proxy maybe ?
Nicolas
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