iTunes WiFi Syncing: Now With More Fail Than Ever!

I got used to iTunes WiFi Sync being broken, because it hasn't worked right for so long.

But now I can barely sync by cable, either.

It used to be after one Wifi sync, Wifi sync would stop working until I quit and relaunched iTunes, rebooted my device (iPad, iPhone), or sometimes both. Now it does the same thing to me via cable connection -- on both an iPhone 5S running iOS 7 and and old iPhone 3GS running iOS 6.3. iTunes tells me the device cannot be found on the network, EVEN WHEN IT'S PLUGGED DIRECTLY INTO my computer.

What happens next? The only way to get iTunes to recognize the device even by Lightning or USB cable is to quit and relaunch. But at this point, the Quit freezes and I must force-quit to get out and back in again.

This is somewhat less than convenient when my wife or kids are upstairs watching something streaming via iTunes on Apple TV.

I want to say many bad words.

PS I should mention I'm using the latest versions of Mavericks and iTunes.