Well thats weird...
Does it happens that the internal IP addressing its the same as the virtual ap controller is distributing?
On the client can you do
ipconfig /all and really chekc that the DHCP server says the ip address of your dhcp server?
Ifyou dont move anything or configure anything the magic vlan will distribute ips
192.168.10.0 255.255.254.0
The default gateway will be 192.168.10.1 so the dhcp server should be 192.168.10.1... Does it happens that the ip it get from the supposed internal network is in that range??
If that true... then try changing the ip address of the magic vlan to something else that does not exist in your network...
You will see this option under settings on general tab
I tell you this because someone else on the forum had an issue with this in which that When a wireless client tries to reach 192.168.10.1, it would occasionally go to the IAP-135's GUI like it says OCASIONALLY and sometimes it get the correct ip address...