Can you check your router? Somewhere, if it's getting its IP by DHCP by your ISP, there should be "Lease time" or something similar. Can you check if it's set at 1 hour and if you can change it? Do not confuse it with the DHCP used for your PCs. It's possible that your ISP is changing your IP and messing with the connection.
Another thing you can try is to set a static IP on your PC. In a similar way it's possible that your router is changing your PC's IP.
About it working with 430, it might just have been a coincidence. It's hard to believe that a graphic card would mess with networking.
