Open the router in the web interface of your router and look at 'status'
Check the Interface Config to make sure that all interfaces have the correct addresses. The correct addresses for wireless and LAN are in setup instructions.
Check System Log and Kernel Log for errors.
If chillispot is having trouble starting try modifying the /etc/init.d/S80chilli line that says /usr/sbin/chilli --dns1="$(nvram get lan_ipaddr)" to just be /usr/sbin/chilli
Also try logging in via ssh and doing
./S80chilli or ./chilli and see what error messages you get.
If your problem is still not solved please post your setup and symptoms to help and we'll be happy to assist you.