I have five Raspberry Pi cards, three of which are connected via Wi-Fi. On two of those three, the computers appeared to halt at just the same time as I was setting up a new iPad 5. They are all running slightly different versions of the standard OS. It might have been a co-incidence - I have very occasionally seen RPi cards halt, but for two to stop at the same time, and when the iPad-5 was being set up is too much of a co-incidence for me.
By stopped, I mean that the devices would not respond to ping, and there was no flashing activity on the on-board LEDs, nor on the Wi-Fi USB dongle.
It /could/ have been because I had to change the Wi-Fi access point from having a MAC access control list to allow the iPad to be seen, and then back again once the iPad had been configured enough to allow its MAC address to be discovered. It still raises the question as to why only two out of the three RPi cards were affected. They all have the same Edimax Wi-Fi dongle.
Just a little note in case anyone sees something similar.