several Dell 3300 wifi printer server stop working at the same time

I have 4 dell 3300 wifi printer server and they have been working great until recently when all of them would stop working. When I look all of them have the usb and wifi LED light both out. I don't know what could have caused that. They are connected to all different kinds of printers: Dell 1720, dymo turbo writer, zebra label printer, samsung laser print. They are all connected to a linksys wireless-G router that has DD-WRT installed. The router is unaffected. I only have to unplug and replug all Dell 3300 and when they come back online, everything is working again with all 3 lights solid. 

Does anyone have any idea how this could happen? The linksys router is used as an AP only for these printers.