itunes won't open automatically when I plug iphone in

I have recently had a lot of trouble syncing calendars with my iphone. I have done all sorts of restarts etc. One problem throughout (recent) is that when I plug my ipne in, itunes won't start up automatically and sync. I cannot tick the box on itunes saying "open itunes when this phone is connected" as it is pale grey and won't let me. Anyone any other ideas? Everything is updated.

I am on a mac and running Mac OS X version 10.6.7

itunes version 10.2.2 (12)