The same thing happened to me yesterday. Lost all my Apple icons except for all the FireCore ones. I switched from wired to wireless and same thing happens on both connections.
I had a line problem with my sky hub, when it came back on this problem appeared the next time I turned my Atv on.
Although my iPad, iPhone etc said I had a good wifi and broadband connection and tested ok.
I reset my hub and All icons now present.
It may be worth noting that I couldn’t access the iTunes store while this was happening, but all ok after Reset.
Hope this helps
Oh wish I had read this first. I’ve just done a full restore. Didn’t think of resetting the hub. Barking annoying because now Infuse won’t remember where I was up to.