If you've ever been in the situation where your network connectivity is flakier than croissant in a blender - you might be inclined to check someone/something hasn't stolen the IP address of your default gateway. This is probably an easy thing to monitor in Linux (watch "arp -an x.x.x.x" for example) but on Windows it's not that easy. BinaryPlant have a nice tool which provides live updates on any ARP requests and responses it can see on the wire, making any conflicting devices easy to identify. This will be taking place in my essential build toolkit!
Check it out here: http://binaryplant.com/