The other day I was helping a client with an HP Officejet 8600. The printer was connecting fine to the wireless network with either a dynamic or static IP assignment. I could ping it, browse to it, and even change settings through the web console. A-okay.
Then, after just two or three minutes, it completely disconnected from the network. I couldn't ping it or browse to it. The system state LED still read that it was connected and nothing had changed in the unit's config.
It took me some time to narrow down the possibilities. What it turned out to be is the 5ghz wireless signal coming from the wireless router. The 8600 uses a 2.4ghz wireless frequency. When I disabled the radio on the router for the 5ghz network, and exclusively offered the 2.4ghz network, and cycled the power on the router, the machine stayed on the network.
Of course, this action would prevent the higher-speed network from working. Bummer-drag. But it did get the unit online and satisfy the client. I guess that's what matters.