I'm using the 64 bit Mac version of iTunes and my device appears in the sidebar for an instant before disappearing again. I've successfully connected and stored files using iExplorer and so forth, so it's definitely an iTunes issue. Any thoughts?
The best way to resolve issues where a device is not connecting to iTunes is to uninstall and re-download iTunes. This has almost always worked for me and is also high on the list of things to do when troubleshooting this type of issue on Apple's website.
The list details are
If all these steps fail Apple reccomends
Make an appointment with a Genius or Contact Apple Technical Support