Shielding was a problem, but someone pointed out that a few years ago the Whipple Shield was invented and used on Canada's RadarSat to protect from orbital debris. This shield technology may be adapted to an interstellar spacecraft in a very positive way, reducing the mass of the hull, and relieving geometric constraints on its shape. The idea with the Whipple Shield is that the meteorite impacts the first metal plate and punches through. It leaves a hole in the plate, but itself is reduced to a fine particle shower (still high speed) that spreads out with a far larger cross-section. The fine particle shower then impacts a second metal shield doing little or no damage.

Finally a strong description of how this will work! :-D

I have yet to determine if the Whipple Shield is feasible at speeds of up to 30 percent lightspeed. I'll be working on this, so stay tuned...