Getting clipped in and started while going uphill is a problem for everyone and has been for as long as there have been bikes with means of attaching your feet to the pedals. There's little that can be done besides trying to make sure you're in a low gear before you stop, and even then it can be difficult, depending on the grade and your gear. Otherwise, the time-honored method (pending traffic) is to go across the fall line of the hill to get started, then turn back into the hill to continue climbing.
You've discovered why cyclists try to avoid stopping mid-hill if there's any way to avoid it. The one year I rode Hilly Hundred, the first day I got boxed in at the side of the road, mid-hill, when the riders ahead and beside me decided to stop. So I had to stop. And there was no way in the world I could get going again on that hill, and had to walk the rest of it.
Last edited by CraigB; 11-04-10 at 05:22 AM.