iPhoto freezes when iPhone is connected
How many photos are on your camera roll?

iPhoto is dynamically loading all the photos on you iPhone/iPad into your MacBook's memory. This is more-or-less the same thing as loading lots of very big picture files off a USB flash drive, so don't be surprised if it takes a (some times very) long time for large camera rolls. To be sure it hasn't choked on the huge number of files you have, open activity monitor or type top in a terminal window. You'll see a list of (almost) all the tasks currently running on your system. So long as iPhoto is taking a semi-significant amount of CPU time (it takes about 10% at idle on my 15-inch MBP), the process isn't hung and you're fine.