This morning, before my coffee, I plugged in my iPhone to sync and it refused. A moments checking reveled an enormous ‘other’ file. I’ve no idea how it got there while I slept.
To fix this:
Don’t sync the iPhone before your morning coffee. (j/k)
I didn’t want to lose any app or personal info so in iTunes I unchecked everything that wasn’t an app or on the info page. Then sync’d again. This removed the huge other file.
Then I resync’d all the previous items; music, photos, podcasts etc and everything is fine.
I’m not sure what the other file was, some people claim to have found huge photo caches, some large app caches, neither of those make sense in my case. But it’s fixed and the fix was reasonably painless so I’m good with that.