A few questions...
1. What version of code are you running?
2. Do you have other RAPs on other sites working successfully in a similar setup?
3. Has this ever worked?
4. Have you tried another user/client device (laptop or whatever) on this same site?
5. On the controller, run a "show ap debug counters" and paste the information regarding the RAP in question.
The subnet you mention typically is seen during RAP provisioing, or in the event of controller connection instability or failure from the RAP's point of view.
Thanks.