That's the problem. You need to change all the values to match your network. Not just the IP of the computer running mining_proxy.exe.
Mask: 255.255.255.0
Gateway: 0.0.0.0
WEB Port: 8000
Primary DNS: 192.168.1.1
Secondary DNS: 8.8.8.8
Pool ports: 8332,8332
Pool addresses: 192.168.0.9,192.168.0.9
Miners user:pass: my username/password copied directly from slush's page
The third octet of the IP of your computer running mining_proxy.exe is different than the third octet of the Cube.
192.168.1.x versus 192.168.0.x.
You need to change the IP of the Cube to be on the same network. It's the recommended configuration for a beginner. Choose an IP address on 192.168.0.XX that doesn't conflict with something already on your network. Restart the Cube and then access it on port 8000 of whatever IP address you choose.
Example:
192.168.0.42:8000
Then you need to change the other Cube configuration values. So, the new configuration should be:
IP: 192.168.0.XX where XX is an available address on your network; say, for example, 192.168.0.42
Mask: 255.255.255.0
Gateway: 192.168.0.1
WEB Port: 8000
Primary DNS: 192.168.0.1
Secondary DNS: 8.8.8.8
Pool ports: 8332,8332
Pool addresses: 192.168.0.9,192.168.0.9
Miners user:pass: my username/password copied directly from slush's page
Ensure that any firewall on 192.168.0.9 running mining_proxy.exe is allowing traffic on port 8332.
Restart the Cube again and restart mining_proxy.exe.