Executive Summary: if you are experiencing problems with iTunes 11.1.4 randomly crashing or locking up, try disabling WiFi syncing with your iOS devices.
iTunes used to work very well for me–until Apple released version 11.
But even with version 11, my problems were mostly annoyances: very slow response time, unhappy with the new look and feel, etc.
Then came 11.1.4, and I began to have real problems.
First, my iMac began to freeze. This had never happened before, but I didn't associate the freezing with iTunes, as the iMac is nearly three years old, and I just assumed that it was due for some problems.
Then iTunes began to crash. A lot.
Checking the Console error logs, I found a ton of messages like this:
iTunesEntered:_AMMuxedDeviceDisconnected, mux-device:201 iTunesEntered:__thr_AMMuxedDeviceDisconnected, mux-device:201 iTunestid:1359f - Mux ID not found in mapping dictionary iTunestid:1359f - Can't handle disconnect with invalid ecid
Can't handle disconnect with invalid ecid? WTF?
I tried reinstalling iTunes, but when that didn't help, I gave Apple a call. They had me delete cache files and do a Safe Boot, which initially seemed to help.
But within an hour, iTunes was crashing again. So I tried a few more things on my own.
Like reinstalling the operating system (it's Mavericks 10.9.1, if you're interested). None of my efforts paid off, so I gave Apple another call.
This time the tech guy had me delete a few more cache files, and do a few more types of booting, etc. When nothing seemed to help, he suggested that perhaps one of the plugins that I use with my web browsers might be the problem. Say What?!
Oh, I did suggest that there might be a problem with the version of iTunes, but he claimed that there were no reports of crash problems with this version. Huh?!
Anyway, I decided to try a few more things on my own, but when nothing seemed to help, I went back to more intensive Googling. Eventually, I found some references to this kind of error message:
com.apple.usbmuxd_SendAttachNotification Device bx:ex:x6:xc:xe:x2@fe80::bae8:56ff:fe9c:ee82._apple-mobdev2._tcp.local. has already appeared on interface 4. Suppressing duplicate attach notification.
And it turned out that I had those messages as well. Apparently they refer to iTunes trying to establish a WiFi connection with an iPad or iPhone, and since the Mac addresses did match my iOS devices, I decided it was worth disabling the WiFi syncing.
Success at last!
In retrospect, the WiFi syncing has been flakey ever since iTunes 11 came out, so it should have occurred to me sooner. Oh, well, better late than never.
But what the hell is wrong with Apple's tech support?
Update 3/15/2014: Disabling WiFi syncing didn't solve the problem entirely. iTunes continued to crash, maybe once or twice a day, which was manageable. However, a few days ago Apple released Apple TV update 6.1, and after installing that, my iTunes crashes seem to have vanished entirely. Good riddance!