Default Gateway disappearing after reboot

This is an interesting problem. It's a possible bug after applying Vista SP2.

Symptoms:
Manually added Default Gateway disappears upon reboot.

Cause:
Null or empty line in registry key "DefaultGateway | REG_MULTI_SZ"

Solution:

1. Start Regedit
2. Navigate to  HKLM\System\CurrentControlSet\Services\Tcpip\Parameters\Interfaces\
3. Select CLSID of network adapter (you can identify your adapter by looking at the IPAddress registry Data field). 
4. Doubleclick "DefaultGateway" (You will see a list of all gateways that disappeared, especially if you've tried multiple gateways and rebooted a few times). Very likely the first line will be blank or empty. Remove this first empty line, click OK, exit regedit and reboot.