Much more information would be needed in your particular situation... assuming you are not using exactly the same router with exactly the same setup? it may be worth it for you to start a new thread to possibly get some more attention towards the issue, and provide as much information as you can about your setup, with model #s, and any troubleshooting steps you have already attempted.
Update: Looks like I spoke too soon. The problem came back, even with wireless isolation enabled. :/
As a temporary measure, I tried enabling "wireless isolation" on the router which prevents any wireless device on the network from talking to any other device on the network with the exception of the gateway to the Internet. Sure enough, my blades started mining again.
I'm going to keep wireless isolation enabled in the meantime while I research a better solution. (I'd like wireless devices to be able to communicate with each other, my network printer, file server)
I haven't looked at specific products yet but I'll probably either replace my current router with one that has VLAN support and then place the port connecting the dumb switch with mining hardware on a separate VLAN from the rest of the network, or get a wired VLAN-capable router (probably cheaper) and use my current router simply as an AP. (my current router has pretty nice wireless capabilities)
I never found this topic last time I had this issue so I ended up posting here: https://bitcointalksearch.org/topic/m.2458852
Wireless router: NETGEAR AC1750
Switch connected to router: NETGEAR GS-108
Mining room switch (connected to other switch): TRENDnet TEG-S16DG
I'd start another topic but all the evidence so far leads to this problem being the same as OP's.
Thanks so much for the info! I never liked the idea of anyone on the network being able to access my mining hardware but I guess now there's a concrete reason to upgrade my network.