I know that you've found a solution to the problem but wanted to point out that if your IP address changes via a change in your router you should expect to be disconnected.
Think of your IP address as your home. If you changed your address without telling anyone your new one, all of your mail would still be going to your old house and not your new one. As such, your applications can no longer communicate using the old connection information which is no longer valid. Some applications can gracefully check their status and then reconnect if a problem is detected and you probably wont even know they have done so. Others may need to be manually restarted or reconnected.
The same thing also happens with hibernation and sleep modes because those are basically like shutting your computer off. When you enter hibernate or sleep modes, they save the state that 'i was connected when i turned everything off' but when they try to communicate with the server after being turned back on they realize that the original connection is no longer active or valid.
Anyway, just thought you might want to know why it happens.
