Just joined this forum, forgive me if I am posting this response in the wrong area. Noticed a 'ton' of people who have their connections dropped. I have an MP640 and had the same problem. Here is the one and only thing that fixed my problem and hopefully some of yours also.
I live out in the country and we have storms that knock out the electric probably 7 or 8 times per year. It is the quick surge that does the most damage; you just notice a quick light flicker and that's all. The computer, router and printer all go down at the same time, but the router is the last to fully reboot. So now you have a printer with all its proper lights on, in all appearance, it is ready to go, BUT IT IS NOT!.
Shut the printer and router off. If you don't have an on/off switch at the back of the router, then disconnect from the wall outlet.
Restart your router, making sure that ALL of your lights are on. My old router took approx 12 minutes to start up, my new one only 3 minutes. Then restart your printer. This solution has worked everytime I had a printer network problem. Good luck,
SailorGeorge PS: Hope this helps some of you.