For no apparent reason my wife's iPhone recently stopped showing up in iTunes on her Mac and the iPhone Troubleshooting Assistant (iPTA) didn't help.
For anyone that hasn't used the iPTA before, this is a handy web based guide that steps you through the common problems and fixes. Things like frozen iPhones, call connection issues, Mail setup and not appearing in iTunes.
Unfortunately, in this particular case it didn't work (including restart iTunes, the Mac and re-installing iTunes).
After searching through Apple's Discussion forums (the #1 place to track down a problem) a few post came to light of people suffering similar problems. The solution seems to be a more thorough re-installation of iTunes, including a proper removal of the Apple Mobile Device Support extension and receipt file.
This process was much quicker than trying the step by step process of the iPhone Troubleshooting Assistant and it worked.
So if the iPTA doesn't solve your problems may I refer you to article HT1747 of Apple's Knowledge Base.
I've been described as a lost technocrat or a wondering luddite, personally I just like everything that takes us forward.