So I had the same problem as you had and I solved by disconnecting my iPhone and then delet the files in /var/db/lockdown as well as delete all the preferences files for itunes under /Library/Preferences.
After this I restarted the computer and when it was up running again I connected the iPhone.
If this doesnt work go through the first step and also start up the phone (chose language, connect to wifi (or not connect, it depends if you have that possibility) etc) so that it is up running without the start guide still active.
Then when this is done with the phone connect it to the computer.
Hope this will work for you as well!
Try hitting the power button and holding down the P key R key and command and option key until you hear a chime 2x on startup. This resets your pram which often solves issues.
I also recommend cleaning up your permissions in disk utility.
I did the delete/var/db/lockdown part and it didnt work until i did a restart then wen i connected my iphone it worked. There may be something to not connecting the iphone till itunes is all up and running too.
I have this same thing--when I reinstall iTunes, it works, but only until I put the computer to sleep and/or reboot, and then the same old problem comes back. Deleted the lockdown folder stuff, no help. Repaired permissions, no help. Reset PRAM, no help. I have an iPhone 5, but had the same problem with my old iPhone 4. Have had this problem for a year and a half now. Have gone through half a dozen versions of iTunes upgrades, no help. The only thing that works is having a virtual Windows machine in Parallels with iTunes in there, except that's a horribly janky solution. Since when does Windows work better than Mac? Come on, Apple! Where's your support?!?
so I have read all of this and I have no, /var/db/lockdown on my computer. I even tried to reload itunes and nothing works. Cannot sync my phone or my ipad. Just keep getting the same message. HELP if you can.. Here is the message: iTunes could not connect to this iPad. Could not allocate a resource.