It's most likely a bad connection. My ISP isn't very reliable and, over the past week, I've had a lot of trouble staying connected to various online programs.
I suggest calling your ISP and asking if there are any problems with the network in your area, and perhaps have them come check your house for any problems. If not, I would try, if in case of you having a wired connection, replacing your Ethernet cable. And if that doesn't work, consider upgrading to a new router. I recently got a Linksys E3200 and am quite happy with it.