No problem, you can set the secondary IP on the proxy machine itself, not through the router. On Windows 7 you do this by going to network and sharing center -> change adapter settings ->  Right click adapter being used -> properties -> select IPv4 -> properties -> advanced -> add IP address. The primary IP has to be static in order to add another, I would recommend using static IPs anyway. You can set the IP to static on the main IPv4 properties page of the adapter. You may also have to change the DHCP pool range on your router, for example, I have my DCHP pool set tp 192.168.1.2 to 192.168.1.199 and my proxy has IPs of 192.168.1.200 and 192.168.1.201.

I recently had the same issue running one cube. I fixed it by adding a secondary IP address to my proxy machine and pointing the backup pool in the cube config to that address. Check out my thread for more info  https://bitcointalk.org/index.php?topic=418856.0

Fixed the problem. Apparently the cubes don't like having the same address for the primary/backup pool, so I gave my proxy machine a secondary static IP address and pointed the backup pool address to that IP. It still switches back and forth between pool addresses every 6 min or so, but it is mining consistently.

I just got a block erupter cube and it keeps restarting about every 8 minutes. When it restarts, the hashrate goes down to 0 then gradually works its way back up to around 30GH. At about 6 minutes, long poll goes inactive, pool begins to switch back and forth between A and B (although they are the same), and stratum proxy stops outputting work request and share accepted messages and starts outputting messages like this:
At about 8 minutes, the cube restarts and does the same thing again.

Here is how I have the system configured:
cube powered by corsair 750 psu with nothing else powered by it. Cube is set to low clock and has its default address of 192.168.1.254:8000. Cube is hardwired directly into the modem/router. Proxy PC is a Windows 7 machine running stratum proxy with default settings to Slush's Pool. It is also hardwired directly to the modem/router with a static IP of 192.168.1.200. Router has an IP of 192.168.1.1. Cube settings are as follows:

IP: 192.168.1.254
Mask: 255.255.255.0
Gateway: 192.168.1.1
WEB Port: 8000
Primary DNS: 192.168.1.1
Secondary DNS: 8.8.8.8
Pool ports: 8332,8332
Pool addresses: 192.168.1.200,192.168.1.200
Miners user:pass: myuser:mypass,myuser:mypass

My initial thought is a proxy issue but I'm not sure what would be causing this or how to fix it. Any help would be greatly appreciated.

You would most likely spend more in power than you would make mining with your CPU and GPU. You could, however, run a usb miner on your laptop and get higher hashrate.