I have a new MacBookPro (my first) and loaded LRCC with no problems. Every time I connect a USB card reader with LR open I get a pop up window asking me if I want to use iPhoto (yes, no, or always). I NEVER want to use iPhoto but can't figure out how to get rid of the splash screen. Do any of you Mac users know how to do this?
Open iPhoto, choose iPhoto > Preferences, and change the Connecting Camera Opens setting.
After you make this change you don't have to open iPhoto again.
More info here:
Additionally, in Lightroom preferences (see the Import Options section below) you can change whether Lightroom opens its own Import dialog box when you connect a camera or card.