If it still connects after that, the only reasonable conclusion is that somebody else in the home is setting it back up because an HDDVR cannot guess your new internet password. If it tries to connect on its own (even unsucesfully as it cannot know what you changed your password to) then after resetting network defaults to unplug the power cord from the HDDVR for 15 - 30 seconds to make sure nothing stuck in some residual memory.
Make sure you are resetting to network defaults through the menu mentioned above as that tells the HDDVR to forget the current connection settings. This usually happens when you’ve connected your Mac to other wifi networks in the past. Re-joining a network every time you wake up your Mac is one irritating thing.
For example, if you dont want the phone to connect to it automatically. &0183 &32 When you wake your Mac up from sleep, you might find that it disconnects from the wifi. Also make sure you don't have a guest connection open on your Wi-Fi network. You can make the phone forget about the details of a Wi-Fi network that you added. Many routers in their settings can deny devices you choose from being allowed service. So I would verify password change was successfull (on both the 2.4Ghz and 5Ghz if your router supports both). No device can automatically know what you have changed your password to. Turn off the SSID Broadcast feature in the Security section of the control panel to prevent unauthorized users from detecting your wireless network.If you have changed your router password but your HDDVR still can connect, there is a big concern. Additionally, change the SSID name to something difficult to guess but easy to remember. Create a wireless key or password that authorized users can enter on their computers before being able to connect to the network or surf the Internet through the wireless router.