This is a hit or miss kind of problem. After upgrading to Lion, some users have had difficulty syncing their iPhone, iPod touch or iPad. The twist is that whereas their iPad won’t sync, for example, other idevices will. Well, here’s a fix that might work.
According to OS X Daily, iTunesHelper is a program from Apple that runs in the background and monitors for idevice connections to your Mac. When an iPad or iPhone is detected, iTunesHelper launches iTunes.
That said, if you’re having idevice sync issues, try this fixlet which some users say has helped them: Quit iTunes, open System Preferences and navigate to Users & Groups. Select your user name and click Login Items.
If you see the warning (above), then this fixlet might be helpful for you. Select iTunesHelper and remove it (click the minus sign). Next, you’ll need a fresh copy, which Apple obligingly provides.
Go to the Applications folder, right click on (two-finger tap) iTunes. From the contextual menu popup, select Show Package Contents.
In Contents, navigate to MacOS and then drag iTunesHelper into System Preferences > Users & Groups > Login Items.
Now, fire up iTunes and connect the iPad or iPhone that’s been giving you trouble — find the device in iTunes lefthand sidebar, click it and then click Sync. Are you feeling the love?
As noted, some folks have had luck with this fix. If not you, start with this Apple knowledge base article and good luck…