This usually happens because you have not filled in your DNS information correctly. My computer does this sometimes, too, and it always appears as though the connection was lost. But, it was actually just that the system could not get the hostname resolved to an IP address. If your DNS information is provided by DHCP, contact your internet provider. It could be a problem with their servers. I'm afraid my problem is with the network, though, and I have not found a solution yet.