tl;dr: What could cause a network printer to lose its connection besides the printer or router or cable between them?
I have had a Canon wired network laser printer for years with no issues, but after a point in time a new problem developed - sometimes when I or my husband tried to print (both PCs are Win7 if that matters) the printer driver would complain of a "network board error". Cycling power on the printer would fix it for the time being, but it would recur (usually the next day or so). After putting up with this for several months, we decided that the printer was dying and bought a new printer, a similar but newer model. But the new one did the same thing! I thought back and realized that it may have started happening at about the time I had simplified our home LAN from a wired router and a wireless access point to one robust wireless router (Netgear) that could do everything we needed. I tried a different network cable, but when that didn't solve it, I decided that the our Netgear router must be flaky. It was already out of warranty, so I bought yet another new router, this time a Buffalo. But... yup, you guessed it: The problem remains! It seems to happen after being idle for some time (a matter of hours, I think) - once we have printed something, we can print more with no issues.
The printer is on a fixed IP address (192.168.1.6) as is a NAS drive (192.168.1.3). The PCs are on DHCP, but the router is set to only assign addresses above 192.168.1.10, so as far as I know I'm not having address conflicts. I do have random interruptions to my internet connection (not obvious when just browsing, but enough to kill Skype and SSH), but that has been going on since long before the printer problem (the reason I changed the network layout was to try to fix that) and it shouldn't even be related to this anyway - the PCs and printer are simply on the internal LAN, and the printer is sitting on the shelf right above the router and is directly connected to one of its LAN ports with a short cable. I can't figure out what else to try! Any ideas?
EDITS: A suggested in the comments, I tested connecting the printer directly to my computer with a LAN cable for a week, and there were no problems, so it's definitely not the printer itself but something in the mysterious bowels of my LAN. I tried to use Wireshark as suggested in other comments, but it doesn't see the traffic between the router and printer (promiscuous mode doesn't work on Windows, apparently). The problem might be happening after some device goes to sleep and wakes up, or leaves the LAN and returns, but I haven't been able to identify a repeatable pattern.
