The `fix` is a byproduct of MSN Messenger's repair sequence, which includes release/renew of your IP address in the same way clicking Repair when you are in the Network Connections/Properties dialogue box for your particular internet connection will take the same steps. So, Messenger is not the issue. And no, you won't lose any contacts due to a dropped connection.
How are you connected to the 'net? Wireless, ADSL, cable, dial-up?