oneillb, typically wifi errors like yours are due to arp protocol issues.
I don't know how to explain the cause, but basically the router loses the indication of the mac address of the box, which becomes unreachable.
I solved it by increasing the frequency of beacon signals.
For example in my router (dlink 3782) the option is called
Signal-Interval: Set the rate at which your wireless network is advertised. The default is 100 milliseconds
I hope it will be useful