|Does the switch have logs? Have you looked at these, and the logs on the computers to see what is happening? Ultimately, if these do not provide the information, you might have to put a packet sneffer on the network to see exactly what DCCP packets are being sent, which device is responding to them, and what that response is.|
On the face of it it doesn't really make sense that adding a router to the network with DHCP disabled would cause devices to release or renew their DHCP leases.
But , let's face it, you have given us very little information to go on. For example:
1. What is your full network topolgy. Other than this switch and wireless router, what other devices do you have? How are they interconnected.
2. What network ranges exist on your network. Presumably the network router is providing access to a different subnet than the rest of the network.
3. What exactly do you mean by "releasing their IPs"? Do they end up with any address at all? If so, which subnet is it on.
4. How are these computers connected to the network? Wireless or wired?
5. Does this only happen when you reboot the devices, or does it happen to active devices as soon as you connect the wireless router?
6. Does it happen to all devices on your network or just some?