iTunes fails to sync

I just bought a new iPhone. I'm trying to sync music to it. iTunes get stuck in "Waiting for changes to be applied..." for what seems like an endless period of time.

Furthermore all of the songs appear on my phone, but they have the cloud icon next to them, which means they aren't actually present on the phone, only the metadata is.

Photos and other data syncs without a problem.

I've tried unchecking the "Sync Music" button in iTunes, but now it still hangs.

How do I even start to figure out what's gone wrong? Does iTunes have crash logs or something?

edit The following message appeared in my Console: 12/18/14 09:49:39.223 AppleMobileDeviceHelper[2164]: 2164:2072015632|AppleMobileDeviceHelper.m:_getDisabledDataClassNamesFromLockdownForTarget| ERROR: Could not find a device with the target identifier d595ce677d5209b98bbdfcfba7d0b020388da8cb. Assuming there are no disabled data classes.

The device is plugged in to my laptop directly (no 3rd party USB adapter)

You are SO not alone in this. Apple are a disgrace. Their 'updates' have rendered useful devices almost useless. I can now no longer sync calendar, photos, music or apps. iTunes just crashes at step 6 'copying'. Have reinstalled iTunes (ms7-64bt), have reset iphone5s (and lost a heap of stuff in process). iPad exactly the same but am keeping it well away from iTunes for now. Total b****dy shambles.